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Biomedical subjects

V Novák

Publications and source records attributed to V Novák.

At least 19 recordsLinked to original sources

[The orbital implant after exenteration of the orbit with the preservation of the eyelids and the conjunctival sac].

In ophthalmology, the orbital exenteration presents the most mutilating surgical procedure. The surgical technique presented by authors, preserves the eyelids and conjunctival sac. This surgical procedure was suggested and repeatedly performed in adult patients with extensive benign tumors (mostly meningeomas) by J. Otradovec and J. Safár. The enucleation of the eyeball preceded this type of surgery. The final state made it possible to put the prosthesis into the conjunctival sac. Today we inform about further development of this surgical technique and according to our own experiences we widen its indications to some malignant tumors (rhabdomyosarcoma and metastases of the retinoblastoma, etc.) in children. The initial cutaneous incision starts in the eyebrow area and is directed toward the bone of the orbital rim. The preparation of the tissue underneath the intact conjunctival sac to the lower aspect of the bone orbital rim follows. After folding the conjuctival-cutaneous sac back, the real content of the orbit is exenterated in the classical manner. After the hemostasis in the orbital apex, the flap is returned to its primary position and suturing of the primary incision in anatomical layers terminates the surgery. The authors refer about a boy, now 17 years old, who underwent at the age of three years the exenteration of the orbit in this manner due to a rhabdomyosarcoma. The authors also refer about the development and application of a special type of prosthesis made from silicone rubber--implant grade--filling out the orbital space and forming the anterior segment of the eye. The prosthesis was created from a classical orbital implant, regularly used in enucleation surgery and a conjunctival implant, a convex-concave plate with diameter of 20 mm. Both parts are made from the same type of silicon rubber and were connected together by vulcanization. The orbital implant was eliptically extended according to the measurements of the orbital casting made from dental impression matter. The cosmetic part, simulating the colored iris and the pupil, was prepared from a polyester sheet, painted with acrylic paint. It was fixated on the conjunctival prosthesis and covered with a transparent silicone foil. For the first time, the prosthesis was applied at the age of seven years, and during the next ten-years period, it was three times exchanged mostly for a bigger model. This procedure guaranteed proper growing of the orbital area and symmetrical development of the face. The prosthesis also carries out the prosthetic role and cosmetically it looks similarly like after the enucleation without the implant.

Child, Preschool↗

Electrocardiographic body surface maps (BSM) in patients with ischemic heart disease examined by coronary angiography.

ECG body surface maps (BSM) is one of the noninvasive methods for the detection of ischemic heart disease. In the present work we registered the BSM in 25 patients, 18 men, mean age 56.8 (31-83) years, 7 women, mean age 58.7 (43-72) years with coronary artery disease and in 23 healthy persons, 17 men, mean age 55 (46-60) years, 6 women, mean age 57 (42-70) years. Using diagnostic system Cardiag we measured 32 parameters of heart electric field (ECG, VCG, isopotential, isointegral, and isoarea maps). The results of BSM examination were compared with the results of coronary angiography (CAG) and other noninvasive methods. Twenty-four patients were BSM positive, 5 of them with negative CAG. In one case both BSM and CAG were negative. None of persons with positive CAG were BSM negative. The values of positive BSM in patients with negative CAG approached more to the values of positive CAG persons than to controls. Despite of small number of persons examined in our study one can conclude that the BSM method detects the damage of myocardium by another way than the CAG.

Adult↗

[Anophthalmos--a conjunctival implant].

The authors submit information on the completed development of a conjunctival implant and its use for modelling of the conjunctival sac in inborn and acquired anophthalmos. Plastic solution in inborn types is used for cosmetic reasons in unilateral degenerative and consecutive anophthalmos. The orbit and adnexa are usually only little affected. The other indication is secondary anophthalmos after enucleation of the bulbus when the conjunctival sac is threatened by retraction due to actionotherapy of the orbital area or a scarry process after a previous injury. The implant is a convex concave circular-shaped plate with a diameter of 20 mm the centre of which is thinner to facilitate manipulation during insertion. It is made from silicone rubber which has properties characterized as implant grade. Before the implantation proper the plate is adjusted by cutting to the desired size. The surgical procedure proper in inborn anophthalmos involves external canthotomy with gradual preparation of the conjunctiva into the Tenon space in the region of the eyelids to create a broad crevice into which the adjusted implant can be inserted. The operation is completed by closing the canthotomy supplemented by partial tarsorrhaphy using unabsorbable suture. Thus the implant is sufficiently fixed in the newly created ocular space. The silicone inlay is left for 3-6 months to allow epithelization of the surgical site round the implant. In acquired anophthalmos with retraction of the conjunctival sac in the first stage the lower transitory fold is released before insertion of the implant by the cul-de-sac method. The function of the implant is modelling of the conjunctival space in anophthalmos to maintain an adequate space for fornices for later insertion of the permanent prosthesis. The implant is manufactured at present by ELLA-CS.

Anophthalmos↗

Mathematical model of the electromechanical heart contractile system--regulatory subsystem physiological considerations.

The biochemical model of excitation-contraction coupling in cardiomyocyte is presented and the validity of simulations of both physiological and pathological processes is discussed. The model of regulatory and actomyosin subsystems, even if it is rather simple in its regulatory subunit, gives results well consistent with experimental data. Specifically, intracellular free calcium levels ([Ca2+]i) were computed under various states of sarcoendoplasmic reticular Ca2+-ATPase (SERCA2) and compared to experimental findings. Computed results reproduced well both the increase in resting [Ca2+]i level and the attenuation of [Ca2+]i decline commonly observed in heart failure. Thus the computational simulations could help to identify core relations in studied systems by comparing results obtained using similar models of various complexities.

Actomyosin↗

ECG body surface isointegral and isoarea maps (BSM) in 30 and 60-years-old healthy humans.

ECG body surface isointegral and isoarea maps (BSM) are the sensitive indications of local electrical depolarization and repolarization changes both in controls and in coronary artery disease. In the present work the absolute values of maximum and minimum (extremum) in BSM have been compared in 24 healthy persons (20-36 years) with 18 older ones (54-70) of both sexes, non-smokers and without cardiovascular diseases in their medical history. Twenty-nine parameters of the heart electric field were registered by 96 unipolar electrodes placed regularly on the thorax and analyzed by the system Cardiag. A lower heart rate and a longer QT interval were found in older persons. The maximum (extremum) of isointegral and isoarea maps was less positive and the minimum was less negative in the older than in the younger subjects (p < 0.01). The maximum Q-wave amplitude on surface thorax was significantly lowers in older than in younger persons. The results confirmed the age-dependent decrease of QRS and T wave potentials.

Adult↗

[Effect of a 10-day animal fat-free diet on cholesterol and glucose serum levels, blood pressure and body weight in 50-year-old volunteers].

The morbidity and mortality of cardiovascular diseases is high in developed countries including Czech Republic. The lifestyle decreases it in 50%. The aim of this work was to ascertain if the short lasting stay without stress and with vegetarian diet (without eggs) and physical activity is able to decrease the main risk factors of cardiovascular diseases. In 106 volunteers, mean age 49.1 (+/- 14.1) years, 83 women and 23 men, the body weight, blood pressure, serum cholesterol and blood glucose (Accutrend GC, Boehringer, Mannheim, BRD) have been measured before and after the stay at the same conditions. Eighty persons were healthy, seven persons with essential hypertension, eight persons with ischemic heart disease, four persons with diabetes mellitus and seven persons with other than cardiovascular diseases. In some persons the lipid spectrum was measured. Cholesterol decreased in blood serum from 4.9 to 4.3 mmol/l (11%--p < 0.01), blood glucose decreased from 4.2 to 3.3 mmol/l (p < 0.05), blood pressure systolic from 121.5 to 117.4 mm Hg (p < 0.01) and diastolic from 76.5 to 73.8 mm Hg (p < 0.05), body weight was not significantly changed. Our results showed, that 10-days lasting stay containing vegetarian diet and physical activity decreased the risk factors of cardiovascular diseases in 50 years-old volunteers.

Blood Glucose↗

[Surgical treatment of recurrent urethral strictures in males after unsuccessful operations].

BACKGROUND: Subvesical obstructions of any origin represent a frequent and serious disorder occurring predominantly in males. Often it brings incontinence and/or erectility dysfunction, infection of urinary tract. Relapses of the acute pyelonephritis can turn into chronic tubulointersticial one and terminate in the renal insufficiency. To treat strictures, dilation, intermittent catheterization and recently stent introduction were used. Most suitable appears a stent from composite polymers. The aim of our work was to test properties of stents developed in the Institute of Macromolecular Chemistry ASCR. METHODS AND RESULTS: Stents from composite polymers, which are non-toxic, not-irritable can swell in body fluids and have mechanical properties similar to that of silicone rubber. Properties of the material are functionally graded and the casting or repoussé from the material can subsequently change its shape. Ten patients (males, aged 25 to 78 years) with long urethral strictures in its bulbocavernous part (50%) were treated with this method. Strictures were caused by pelvical fractures (4 times), prostate hypertrophy surgery (4 times), prolonged catheterizations (2 times). All patients were followed for 16 to 26 month and had no severities. CONCLUSION: Our results indicate that stent from composite polymers and silicone may have long-acting effects without irritation or crust formation and beneficially effected healing of the spongio-fibrous process.

Adult↗

Intubation of the lacrimal pathways under endoscopic control.

Described herein is a new modification of the lacrimal pathway intubation in children with efferent lacrimal pathway obstruction. For removal of the intubation set probe without olive tips from the inferior nasal meatus, a special titanium loop is used. An endoscopic technique allows us a basically more considerate performance of this procedure and to speed it up. The risk of iatrogenic damage to the mucous membrane of the inferior meatus is, thus, reduced too. From April 1994 to June 1998, lacrimal pathway intubation was performed in 235 children 283 times. Infraction of the inferior concha was performed 27 times. Insertion of a probe submucously into the inferior nasal meatus was found 35 times and the probe was released by focused incision of the mucous membrane.

Adolescent↗

Development of fixable stent for long-term derivation of lower urinary tract.

The object of the envisaged project is the development of easily fixable non-irritant stent of the lower urinary tract. The project has the aim to remove the obstruction and make passage-way through urethra which, after repeated operations, remains narrowed and requires repeated dilatations or, in the patients who have a chronic epicystostomy due to the non-passable urethra. The prosthesis must be self fixable, non-irritant, easily introduceable and removable by endoscopy, enabling normal urination with urinary continence and, last but not least, at a reasonable price.

Equipment Design↗

[Biodegradation of silicone in voice prosthesis].

The most important problem of the useful life of vocal prostheses is bacterial and especially mycotic colonization of their surface which impaired tightness of the closing valve of the prosthesis and caused subsequent leakage of fluids and food into the airways. The objective of the present study was to prevent colonization of the silicone surface and to prolong the service life of the prosthesis. The implanted prostheses were examined under microscope after varying intervals in vivo. The silicone of the implanted prosthesis was colonized by numerous microorganisms, in particular moulds. Seventeen bacterial and mycotic strains were identified. They behave to Candida, Acinetobacter, Micrococcus, Pseudomonas, Bacillus and Chryseomonas. The results confirmed the deep degradation of silicone rubber located in islets. Plant of bacterial tissue were inoculated on two types of silicone disks. Two types of silicone were tested (Silastic Q7-4550-50ShA and Q7-4765-65) after 4, 8 and 12-week exposure. Neither of these materials was attacked by mycotic agents in vitro. Only frame print was appreciable in five hundred times magnification. The second object of the study was to recognize the main degradation factor that means a kind of microorganism. The ability of microorganisms to assimilate oligo- and polyorganosiloxans was studied. Candida albicans does not seem like a typical microorganism assimilating silicon rubber. The results of our study proved Microccus as a typical vector which assimilates silicone.

Bacteria↗

[Biodegradation of silicone drainage tubes in the efferent lacrimal system].

The authors present an account on their experience with biodegradation of silicone cannulas used for drainage of the efferent lacrimal system. They examined by means of a light microscope (enlargement up to 140 x) 38 cannulas, inserted into the lacrimal pathways for 1-7 months. They did not observe any biological damage of the surface of the cannula, not even when compared with non-exposed cannulas. Microbiological examination of six exposed cannulas did not reveal fungal infestation. The lacrimal pathways are not an aggressive environment for temporary cannulas.

Bacteria↗

[Initial experience with the Jones method of conjunctivo(dacryo)cystorhinostomy].

In obstruction of both lacrimal ducts at present the most frequently used method is conjunctivo(dacryo)cystorhinostomy using a Jones bypass cannula. The effectiveness of the procedure is 85-90%. The drainage cannulas can be straight or bent and are as a rule made from pyrex glass. The patients should be highly motivated and made familiar with possible complications, i.e. most frequently escape of the cannula. With regard to the necessary postoperative cooperation the operation is not recommended in young children. The authors performed in 1996-1997 a total of 8 conjunctivo(dacryo)cystorhinotomies. The lacrimal sac is opened into the nose under general anaesthesia by the endonasal route using endoscopes. In one instance the authors used a straight silicone cannula which fell out after three weeks. In the remaining patients they used a bent silicone cannula. Seven patients evaluate their condition after surgery as markedly improved and would be willing to have the operation again. One female patient (after escape of a straight cannula and later reinsertion of a bent cannula) would hesitate to have another operation. The authors evaluate their experience with this type of bypass operation as very satisfactory.

Dacryocystorhinostomy↗

[Intubation of afferent lacrimal ducts--a review of techniques].

The authors present a review of various techniques of long-term intubation of efferent lacrimal pathways by a silicone fibre. They use an original way of intubation and intubate the insertion probes of the intubation set from the lower nasal outlet by means of a titanium loop under direct optic control by means of an endoscope. The use of the endoscope makes it possible to reduce the number of complications and iatrogenic damage of the mucosa and it enhances the effectiveness of the procedure. The authors prefer the use of special intubations sets; for young children intubation sets made from soft metal are preferable. At present all their demands are met by the intubation set they developed in collaboration with the Technical University, Prague. During the period between April 1994 and August 1996 the authors used the described technique for bicanalicular intubation of the efferent lacrimal pathways in 127 children and in adult patients 6x. In 86 instances they used an intubation set of Geuder Co., 44 times their own intubation set.

Adult↗

[Cannulation of congenital lacrimal duct obstruction].

During the development of a Czechoslovak silicone cannula for reconstructive surgery of the lacrimal passage-ways was elaborated the modification for the congenital obstruction. The surgical method imoles the probing and cannulation at the same time. probe with fixed cannula passed delicately through nasolacrimal duct via the upper or lower canaliculus to saccus lacrimalis. This probe overcomes the lateral part of the nose on the inspection of otorhinolaryngologist. The end of cannula was fixed by the stitch to skin near lacrimal punctum. The silicone tubing is left in situ for about three months.

Humans↗

Changes of the inner time structures in the sequences of interspike intervals produced by the activity of excitatory and inhibitory synapses: simulation with Gaussian input processes.

The computer simulation of space-temporal summation of post-synaptic potentials of neurone's membrane demonstrated the outstanding changes in the inner time structures of generated interspike intervals. The output time series of ISIs were studied using non-standard kind of time analysis -- recurrence plot method. Using this technique we observed phenomenon of unification in inner time structures of output series. Further we identified such parameters of model which exerted the most considerable influence on this phenomenon.

Action Potentials↗

[Use of the recurrence plot method in stochastic analysis of neuronal activity].

The recurrence plot method is described together with its application to the analysis of inner time relations in the sequences of interspike intervals. The depicted method was employed to analyze results from the computer model of the neuronal stochastic activity. It can be also used to analyze sequences of interspike intervals in the records from life neurons.

Action Potentials↗

A model of stochastic activity of neurone in some types of Gaussian input processes.

A new approach to computer modelling of neuronal stochastic activity is described. The output dynamic activity which depends on the types and the number of input synapses, weights of the synaptic efficacy, the absolute refractory phase duration and threshold level is evaluated on this model in some types of Gaussian input processes. The behaviour of this model for one excitatory and one inhibitory synapse is described in dependence on the changes of excitation weight. The neuronal behaviour presented depends on the number of interspike intervals and the excitation weight and interspike interval density distribution. A novel concept of the e-curve is being introduced, which shows the dependence of the number of output interspike intervals on the weight of excitation on a stable inhibition level, the absolute refractory phase value and the threshold level. The properties of e-curves are discussed. Furthermore, examples of transformations of input stochastic processes are mentioned from the aspect of density distribution changes of interspike intervals.

Computer Simulation↗