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Biomedical subjects

J Strnad

Publications and source records attributed to J Strnad.

At least 19 recordsLinked to original sources
PubMed1995

Identification of a critical aspartate residue in transmembrane domain three necessary for the binding of somatostatin to the somatostatin receptor SSTR2.

To determine which residues within the rat somatostatin receptor subtype SSTR2 may be interacting with the lys9 of somatostatin-14 (S-14), mutant SSTR2 receptors were created by mutating asp89 or asp122. [125I Tyr11]S-14 binding to D89A and D89E mutants suggests that asp89 is not directly involved in S-14 binding. Binding studies with the charge switch mutants, asp9S-14, and D122K, suggest that asp122 may be interacting with the lys9 of S-14. [125I Tyr11]asp9S-14 displayed saturable binding to D122K with an affinity comparable to that seen with [125I Tyr11]S-14 and WT SSTR2. These data suggest that the interaction between lys9 of S-14 and the TM3 asp122 of SSTR2 represents one contact site between S-14 and SSTR2.

Animals↗
PubMed1994

Rat somatostatin receptor type 1 couples to G proteins and inhibition of cyclic AMP accumulation.

The pharmacology, signal transduction, and coupling to G proteins of the rat somatostatin (SRIF) receptor (SSTR)1 have been characterized in transfected Chinese hamster ovary (CHO) (K1 strain) cells. The expressed receptor exhibited saturable, high affinity binding of several radioiodinated SRIF analogues. Three different radioligands were used to determine the pharmacological properties of this SSTR subtype. [125I-Tyr11]SRIF-14 (125I-S-14), [Leu8,D-Trp22,125I-Tyr25]SRIF-28 (125I-S-28), and cyclo(D-Trp-Lys-Abu-Phe-MeAla-125I-Tyr) (125I-peptide C) displayed the following rank order of affinity (Kd) for the SSTR1 subtype: 125I-S-14 > or = 125I-S-28 > 125I-peptide C. Competition of 125I-S-14 with S-14, S-28, or peptide C displayed the same rank order of potency. Chemical cross-linking of specifically bound 125I-S-28 to membranes from CHO cells expressing the receptor indicated that the molecular weight of the SSTR1 expressed in CHO cells is approximately 70,000, suggesting that it is heavily glycosylated. Previous reports have suggested that the human SSTR1 [Mol. Pharmacol. 42:28-34 (1992)] couples poorly to G proteins. The coupling of the rat SSTR1 to G proteins was demonstrated by three independent methods. (a) Binding of 125I-S-14 to the SSTR1 subtype was inhibited in a dose-dependent fashion by incubation of membranes with guanosine-5'-O-(3-thio)triphosphate. (b) Treatment of cells with pertussis toxin decreased binding by 80%. (c) Immunoprecipitation of 125I-S-14 binding was observed with antiserum specific for Gi alpha 1,2, but not with antiserum specific for Gs alpha, in membranes from transfected cells. In CHO cells transfected with the SSTR1 cDNA, SRIF inhibited forskolin-stimulated cAMP accumulation by up to 50%, in a dose-dependent fashion (ED50 = 1.1 nM). Pertussis toxin treatment decreased both the efficacy and the potency of the SRIF-mediated inhibition of cAMP accumulation (from 50% to 22%), compared with control untreated cells. These data suggest that the rat SSTR1 inhibits cAMP accumulation by coupling to pertussis toxin-sensitive G proteins.

Amino Acid Sequence↗
PubMed1993

The rat SSTR2 somatostatin receptor subtype is coupled to inhibition of cyclic AMP accumulation.

The rat somatostatin receptor SSTR2 subtype has been cloned and expressed in Chinese Hamster Ovary (CHO) cells. Four different radioligands were used to determine the pharmacological properties of this somatostatin receptor subtype. [125ITyr11]S-14, [125ITyr25]S-28, and cyclo (D-Trp-Lys-Abu-Phe-MeAla-[125ITyr]) displayed comparable affinities for the SSTR2 subtype (approximately 100 pM). The affinity of a fourth radioligand, D-beta Nal-cyclo (Cys-[125ITyr]-DTrp-Lys-Val-Cys)-Thr-H2N, was approximately 10-fold lower (approximately 1000 pM) than the three other radioligands. Competition of [125I]S-14 with either S-14 or S-28 also revealed comparable IC50 values (250 pM). In CHO cells transfected with the SSTR2 cDNA, S-14 inhibited forskolin-stimulated cAMP accumulation by 75% in a dose-dependent fashion (EC50 = 350 pM).

Animals↗
PubMed1993

[Stab and gunshot thoracoabdominal injuries].

The authors give an account of their experience with the treatment of punctures and gunshot injuries of the chest and abdomen in 43 patients hospitalized at the Surgical Clinic of the Third Medical Faculty, Charles University Prague 10 between 1989 and 1992. Injuries of the chest were recorded 15 times, abdominal injuries in 25 patients and concurrent injuries of the chest and abdomen in three patients. To ensure treatment of penetrating injuries the authors present an algorithm which comprises differentiated care as well as some non-interventional diagnostic methods (ultrasonography, computed tomography). Based on analysis of their own results and data in the literature, the authors recommend in casualties with penetrating chest injuries and abdominal injuries early indicated surgical revision which alone ensures adequate treatment with minimal diagnostic errors. They also draw attention to the necessity to ensure effective first aid and rapid transport of casualties to prevent the development of irreversible changes as a result of haemorrhage, as observed in a single patient who died after a piercing heart injury.

Abdominal Injuries↗
PubMed1990

In vivo selection of human tumor cells resistant to monoclonal antibody-Vinca alkaloid immunoconjugates.

UCLA-P3 human lung adenocarcinoma cells were grown in nude mice and given repetitive treatments of a monoclonal antibody-Vinca alkaloid immunoconjugate. Although this therapy resulted in a greater than 4-fold reduction in mean tumor mass of the established tumors, some animals experienced a reinitiation of tumor growth after cessation of conjugate treatment. Two such animals were treated again with high doses of monoclonal antibody-Vinca but one of the tumors was no longer regressed by the drug conjugate. The tumor was excised, enzymatically dissociated, and grown in tissue culture. Cultured cells were reimplanted in nude mice and subjected to further therapy with a monoclonal antibody-Vinca conjugate. The resulting tumors were also refractory to the immunoconjugate therapy. This cycle was repeated for a total of three times and resulted in the serial in vivo selection of three conjugate resistant variants. The mechanism responsible for the in vivo resistance of human tumor cells to the monoclonal antibody-Vinca immunoconjugate is unknown but does not appear to involve antigen modulation, altered tumor cell growth rate, or an apparent decrease in tumor targeting in vivo. The resistance was also not accompanied by any detectable elevation in multidrug resistance 1 mRNA or P-glycoprotein expression. Significantly, the resistance pattern was observed only in vivo and was not maintained by cells grown in vitro.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

[Methods of determining clinically sufficient decurarization and its evaluation].

Mechanomyoscopy as an objective method for determining the degree of decurarisation is particularly useful in the case of uncooperative patients and those who are incapable of adequate neck flexion mostly for spinal column diseases. The authors use for that purpose a Czechoslovak-made neuromuscular stimulator (LSN 110), with constant 50 Hz frequency of stimulation, 0.3 ms impulse duration, max. 50 mA and, depending on skin impedance, 5-140 V. The stimulator switch is manually controlled. The absence of muscular fatigue (fade) on single as well repeated stimulation lasting only a fraction of a second necessary to elicit muscular response does not rule out residual curarisation despite the fact that less than 70% of the cholinergic receptors are blocked. The only reliable sign of clinically sufficient decurarisation is the ability of the muscles of the hand to maintain contraction on tetanic stimulation of the motor point of the ulnar nerve in the wrist for at least 5 seconds without fatigue, and that even on a repeated exercise. This corresponds to a block of less than 60% of the cholinergic receptors. The patient's ability to raise his or her head and to keep it raised at 4 fingerbreaths for a period of 4 seconds is also a manifestation of clinically sufficient decurarisation. The value of forced expiratory volume is not conclusive evidence of sufficient decurarisation, it only gives a rough idea of its degree. The final decision is up to the an anaesthesiologist, his knowledge and experience based on objective data.

Adult↗
PubMed1990

[The positive effect of the 10 degree Trendelenburg position in patients undergoing epigastric surgery with lumbo-thoracic epidural anesthesia].

The authors administered to 60 patients, mean age 71 years, epidural anaesthesia on account of operations in the epigastrium. A solution of 0.5% bupivacaine without adrenaline in doses calculated according to Bromage for 18 segments was administered from a lateral approach in the upper part of the lumbar spine. After administration of the anaesthetic they tilted the patients to a 15-20 degrees Trendelenburg position. They adjusted the slope of the patients to ensure that the anaesthesia reached eventually the radicular zone of Th3. They made use of the finding that the anaesthetic solution in the epidural space tends to decline. After fixation of the anaesthetic to the nervous tissue, 30 patients were slowly changed to a horizontal position and the same number of patients was left throughout the operation in a Trendelenburg position. The authors made sure that the systolic blood pressure did not drop below 13.3 kPa in normotonics and beneath 60% of the initial value in hypertonic patients. There were no substantial differences in the ephedrine consumption per kg body weight within three hours after the puncture of the epidural space in the two groups. The total consumption of Hartmann solution, ketamine and diazepam was, however, significantly lower in patients who during operation were in the 10 degrees Trendelenburg position. The variations of blood pressure during traction of anatomical structures in the epigastrium were smaller in the latter patients. No serious disorders of the cardiac rhythm were recorded. None of the patients of the group died within seven days after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1990

[Catheterization of the central venous system by way of the cubital veins].

The authors elaborated and tested in 100 patients the described method and were successful in 97%. After local anaesthesia they incise the skin in the inner portion of the skinfold in the cubital fossa and, if necessary, extend it to the bicipital ridge. The best vein as regards access is the v. basilica or the strongest branch of the brachial vein, on both sides. They isolate the vein and insert a thread underneath it. The ends of the thread are grasped by a forceps and thus the vein is fixed. After compressing the arm with a rubber band with subsequent venostasis they puncture the vein on the index finger with sharp scissors. A polyvinyl catheter cut obliquely at the end with an external diameter of 1.5 mm, containing a drip infusion of saline, is inserted slowly into the vein of the sitting patient without positioning of the head, 40-60 cm centrally, with the free hand. The position of the tip of the catheter is checked by X-ray. If there is a venous spasm (the catheter cannot be inserted, its tip is beyond the thoracic cavity or it forms a loop or is bent) the arm is compressed as high as possible. At a short distance the authors insert a catheter into the vein and administer in a drop infusion 40-60 ml 0.3% Xanidil (xanthinolium nicotinicum) solution. After relaxation of the spasm they connect the infusion with the saline, release the rubber band and complete the cannulation. In case of an unintentional injury of the vein they suture it but never use ligatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Arm↗
PubMed1990

[The role of ultrasonographic examination in the diagnosis of thyroid gland disorders].

The authors compared the results of ultrasonographic examinations of thyroid processes with clinical and histological findings of operated patients. The results proved the importance of ultrasonographic examinations as one in the complex of examination methods before operation of the thyroid gland for the assessment of the preoperative diagnosis.

Humans↗
PubMed1989

[Experience with the lateral lumbar approach in epidural anesthesia].

Based on a detailed analysis of X-ray pictures of the lumbo-sacral spine and experience assembled during epidural anaesthesia in 116 men, mean age 67 years, and 84 women, mean age 68 years, the authors describe in more detailed the formerly recommended method of a lateral lumbar approach. To make it as successful and as safe as possible it is essential during puncture to be aware of the typical resistance of the yellow ligament, frequently after previous contact with bone and to obtain the positive sign of the "hanging drop" after penetration of the ligament. If in exceptional instances in the depth the elastic resistance of the yellow ligament is lacking before the positive sign of the "hanging drop", it is better to perform the puncture of the epidural space in another intervertebral space. This practically rules out the false positive sign of the "hanging drop" in case of the possible presence of a tougher ligamentous septum in the paravertebral muscles in older patients. This rules out also the even rarer possible penetration of the needle to the dura mater, exactly in the middle of the yellow ligament through the opening for the blood vessel where are only individual elastic fibres, practically without resistance, with a positive "hanging drop".

Adolescent↗
PubMed1989

[Differences in patient sensitivity to currently used non-depolarized curaremimetics and factors which affect it].

A whole number of factors which affect the depth as well as duration of the block after administration of non-depolarizing myorelaxants, both positively and negatively. However, the effect in one patient can be predicted only with difficulty--as this paper showed--as neither the hydration level, age nor kalemia concentration had any effect on the depth of the neuromuscular block. Neither in patients, otherwise healthy, is it possible to predict the degree of the neuromuscular block after administering a standard dose of curaremimetic. The depth of the block can only be established by an objective method--mechano-myoscopic block monitoring. For this purpose, the authors use a Czechoslovak-made neuromuscular stimulator LSN 110. The determination of the actual block depth can help to control relaxation according to the needs of the surgeon or anaesthesiologist, and according to the individual patient's sensibility. A different sensibility response to myorelaxants was found in pipecuronium, vecuronium and even in atracurium. It corresponds approximately to gaussian curve of frequency.

Adult↗
PubMed1989

Molecular cloning and characterization of a human adenocarcinoma/epithelial cell surface antigen complementary DNA.

A human adenocarcinoma-associated antigen (KSA) defined by the monoclonal antibody KS1/4 has become the focus of several site-directed strategies for tumor therapy. KSA, a 40,000 Da cell surface glycoprotein antigen, is found at a high density in all adenocarcinomas examined to date and in corresponding normal epithelial tissues. Here we describe the cloning and sequencing of overlapping complementary DNA clones which encode the entire KSA as expressed in UCLA-P3, a human lung adenocarcinoma cell line. We have deduced the 314-amino acid sequence and have compared it to the N-terminal amino acid sequence data of the affinity-purified antigen. The KSA is synthesized as a 314-residue-long preproprotein that is then processed to a 232-residue-long antigen. KSA appears to have a single transmembrane domain of 23 residues that separates the highly charged 26-residue cytoplasmic domain from the extracellular domain. The N-terminal region of the propeptide is rich in cysteines and contains three potential N-glycosylation sites. Computer-assisted analyses at both the DNA and protein levels have found no significant similarities of this protein to known sequences, but a GC-rich 5' terminus is evident. Northern blot analysis shows that transcription of KSA can be detected in RNA isolated from normal colon but not in RNA isolated from normal lung, prostate, or liver.

Amino Acid Sequence↗
PubMed1989

[Traumatic ruptures of the diaphragm].

The authors present a group of three traumatic ruptures of the diaphragm and call attention to the possibility of this injury in blunt injuries of the chest or abdomen. In the diagnostic part they describe the complex character of diagnosis of rupture of the diaphragm even when modern non-invasive examination methods are used, some of which (CT) may give false positive results. The authors describe typical symptoms leading to the diagnosis.

Accidents, Traffic↗
PubMed1988

In vivo effects of recombinant human interleukin 2 on antitumor and antiviral natural immunity in induced or natural murine immunodeficiency states.

We have examined the ability of in vivo treatment of mice with recombinant interleukin 2 (rIL-2) to affect natural immunity measured against tumor (YAC-1) or virally infected (herpes simplex type 1) target cells. rIL-2 treatment leads to significant increases in natural killer/lymphocyte-activated killer (NK/LAK) function and spleen cells recovered. This effect is dose dependent and strain related. The latter parameter correlated with the pretreatment NK activity level of the strain. The rIL-2 induced NK/LAK augmentation is also kinetically restricted as treatment must have occurred within 48-72 h of assay to be effective. The rIL-2 therapy effectively enhances both antitumor and antiviral NK/LAK activity and results in a noticeable increase in asialo-GM1-positive cells in the spleens of treated mice as well as a significant increase in IL-2 receptor expression as monitored by either cytometry or radioligand binding. In vivo treatment of mice with an antibody directed to the ASGM1 determinant effectively reduces the rIL-2 augmentation of both antitumor and antiviral activity even though this treatment does not affect the pretreatment level of antiviral activity. Various natural and induced immunodeficiency states (immunotherapy, irradiation, immunosuppressive drugs, cytoreductive drugs) have been examined for the ability of in vivo treatment with rIL-2 to enhance NK/LAK activity. In vivo rIL-2 administration is differentially effective in enhancing NK/LAK activity in these situations. Notably, in these induced immunodeficiency states, although NK/LAK activity is commonly enhanced, the number of spleen cells recovered often is only marginally affected. Thus, as expected, a limiting aspect in this use of a natural immunomodulator is the number of potentially responsive cells present in the immunodeficiency condition. In addition, correlations between rIL-2 effect, several of the immunodeficiency states, and vascular leak syndrome are briefly discussed.

Animals↗
PubMed1988

A design approach to the structural analysis of interleukin-2.

A semi-synthetic protein design approach has been employed for the structural investigation of a putative helical region at the C-terminus of Interleukin-2. With crystallographic or NMR derived conformational data as yet unavailable, we have relied only on primary sequence information and computer-assisted modelling to direct the analysis. By employing both chemical peptide synthesis and recombinant DNA methods, the C-terminus of IL-2 was modified according to a strategy designed to stabilize helical secondary structure. A semi-synthetic protein incorporating 12 simultaneous amino acid replacements was constructed, which possessed potentiated biological activity and displayed a far UV circular dichroism spectrum comparable to a hybrid protein with the authentic sequence. By comparison, another hybrid protein containing a C-terminal region designed to contain helix breaking residues was totally devoid of bioactivity. These findings provide evidence that the modelling method correctly identified a helix necessary for the formation of a bioactive tertiary fold. Moreover, by employing semi-synthesis it was possible to circumvent the difficulties associated with the preparation, purification and analysis of multiple recombinant proteins, and also to avoid the unreliability of total chemical synthesis for proteins greater than 100 residues.

Amino Acid Sequence↗