Search PubMed⌕ Search

Biomedical subjects

T Hirvonen

Publications and source records attributed to T Hirvonen.

At least 37 records · Page 2Linked to original sources
PubMed1995

A comparison of static and dynamic calibration techniques for the vestibulo-ocular reflex signal.

We investigated two calibration techniques commonly used with eye movement signals pertaining to the vestibulo-ocular reflex. Eye movement signals were recorded electro-oculographically as usual and calibrated using both static and dynamic calibration techniques. The calibration values of normals and patients were computed and compared to each other. Also gain parameters of vestibulo-ocular reflex which depend on the calibration were computed. We found that both techniques are chiefly equally valid, and there are no considerable differences in results computed with either one.

Algorithms↗
PubMed1995

[Heart-related chest pain without manifest coronary disease].

Chest pain is a common reason for consulting a physician. Although the underlying cause of the chest pain varies, the most frequent cause is coronary disease. In many cases the diagnosis emerges from the case history, the clinical picture or non-invasive examination procedures. In cases of severe symptoms or unclear diagnosis, coronary angiography is performed which often shows the coronary arteries to be patent. In a large proportion of these patients the chest pain is of non-cardiac origin. In addition to coronary disease, other heart-related conditions may give rise to chest pain.

Chest Pain↗
PubMed1994

The neurophysiological basis and the role of inflammatory reactions in dentine hypersensitivity.

Recent studies indicate that intradental A-type nerve fibres are responsible for the sensitivity of dentine and are activated by fluid movements in dentinal tubules (hydrodynamic mechanism). The patency of the tubules affects dentine sensitivity to a great extent. Both A delta- and A beta-type nerve fibres respond to dentinal (hydrodynamic) stimulation in a similar way. Only a few studies have been made on the regional sensitivity of dentine or the receptive areas of intradental nerve fibres. The results indicate that the fibres innervating different parts of coronal dentine are equally sensitive to dentinal stimulation but those in the cervical area may be less responsive. Inflammation in the pulp can considerably alter dentine sensitivity. In dog teeth with chronically exposed dentine, nerve responses to hydrodynamic stimulation were reduced although other functional changes indicated nerve sensitization. This may be due to spontaneously occurring changes in the exposed dentine that block the tubules. In acute experiments on cat and dog teeth with open dentinal tubules, certain inflammatory mediators increase the sensitivity of the responding nerve fibres. It seems that intradental C-fibres do not respond to hydrodynamic stimulation of dentine. They are polymodal and activated when external stimuli reach the pulp proper. They could perhaps mediate the dull pain connected with pulpitis. However, they might also have an important modifying effect on dentine sensitivity because they can release neuropeptides, which function in the inflammatory reactions.

Animals↗
PubMed1994

Postpartum diagnosis of placenta accreta with colour Doppler sonography.

Placenta accreta, although uncommon, is becoming an increasingly important clinical problem associated with placenta praevia and previous Caesarean section. A case report is presented of a woman with post partum partial placenta accreta diagnosed with color Doppler ultrasound. The aetiology, risk factors, clinical conditions, treatment and sonographic diagnosis are shortly reviewed.

Adult↗
PubMed1994

Urinary tract fistulas following abdominal hysterectomy.

Sixteen patients with urinary tract fistulas (14 vesicovaginal and two ureterovaginal) following simple abdominal hysterectomy were treated over a period of 17 years. Most vesicovaginal fistulas were treated by a transvesical technique, which proved to be a comfortable and successful method in our hands. Closure of the fistula followed usually more than four weeks after diagnosis. Earlier repair, which has been forwarded as an alternative therapy, might give equally good results and would save the patient from the severe hygienic problem of continuous urinary leakage. Conservative treatment with an indwelling urinary catheter led to spontaneous closure of the fistula in one patient. Two ureterovaginal fistulas were corrected by an anti-reflux ureteroneocystostomy.

Catheters, Indwelling↗
PubMed1994

Comparison of two suture materials, Dexon Plus and Maxon, in abdominal hysterectomy.

The performance and handling capacities of two synthetic absorbable sutures, the monofilament suture Maxon and the multifilament suture Dexon Plus, were compared to study if these sutures are acceptable as all-purpose suture materials in abdominal hysterectomy. Four senior gynecological surgeons performed altogether 102 hysterectomies and made an assessment of handling qualities. Fifty one patients were sutured with Maxon and 51 age-matched controls with Dexon Plus. Maxon proved to be superior to Dexon Plus in terms of knot rundown, tissue drag and knot repositioning whereas, in terms of suppleness, tensile strength and knot security both suture materials were comparable. Vaginal granulation was seen in five patients operated on with Dexon Plus and only in one patient in the Maxon group. According to this study Maxon is as safe and efficacious as Dexon Plus for abdominal hysterectomy and its handling properties were even better than those of Dexon Plus.

Adult↗
PubMed1994

Outcome of thirty patients who underwent repair of posthysterectomy prolapse of the vaginal vault with abdominal sacral colpopexy.

Thirty women experiencing posthysterectomy prolapse of the vaginal vault were treated with abdominal sacral colpopexy between 1984 and 1991. Lyodura (lyophilized cerebral dura mater allograft transplant) was used as the suspensory material in 81 percent and Gore-Tex (reinforced polytetrafluoroethylene) in 16 percent of the operations. There were no perioperative or postoperative complications. At the follow-up examination (mean, three years), good vaginal vault support was observed in 85 percent of the patients. Significant cystocele were seen in 18 percent, and vault prolapse, enterocele, rectocele and chronic perineal laceration each in 15 percent of the patients. At follow-up study, 22 percent of the patients experienced dyspareunia and 41 percent had decreased sexual interest and coital events. Development of stress urinary incontinence in 18 percent of patients was noted. Concomitant Burch colposuspension will cure and prevent stress incontinence and anterior vaginal relaxation. Abdominal sacral colpopexy appears to be a safe and effective method in the treatment of posthysterectomy prolapse of the vaginal vault. In our experience, it seems that coexistent cystocele and rectocele should be corrected in the connection with sacral colpopexy.

Abdomen↗
PubMed1993

Abnormalities in left ventricular diastolic function in male patients with rheumatoid arthritis without clinically evident cardiovascular disease.

Epidemiological studies have suggested that patients with rheumatoid arthritis (RA) have increased mortality due to cardiovascular disease. We studied cardiac performance in 12 asymptomatic male patients with RA and 14 control subjects to elucidate early disturbances in cardiac function. In echocardiography, isovolumic relaxation time was longer (64 +/- 6 vs. 49 +/- 3 ms, mean +/- SEM, P = 0.010) and peak filling rate (134 +/- 10 vs. 159 +/- 6 mm s-1, P = 0.015) lower in patients with RA than in control subjects, reflecting an impairment in left ventricular diastolic function. Left ventricular systolic function assessed by radionuclide angiocardiography at rest and during exercise was similar in both groups. There were no differences between the patients with RA and control subjects in the heart rate, systolic blood pressure and oxygen uptake during peak exercise. Left ventricular diastolic function is impaired in spite of normal left ventricular systolic function in patients with RA without clinically evident cardiovascular disease and this may contribute to the excess of cardiovascular mortality in patients with RA.

Adult↗
PubMed1993

Effects of abdominal hysterectomy on urinary and sexual symptoms.

A prospective study of 102 women undergoing abdominal hysterectomy for benign conditions was performed in order to evaluate pre- and post-operative urinary and sexual symptoms. The mean age of the patients was 44.9 years (range 30-65). Urinary disorders such as urgency, dysuria, frequency, nocturia, slow bladder emptying, sensation of residual urine as well as stress and urge incontinence were observed pre-operatively and 2, 6 and 12 months post-operatively. Dyspareunia, libido and the number of orgasms were evaluated as disorders affecting sexual life. At follow-up 12 months post-operatively a statistically significant decrease in stress incontinence, frequency and nocturia was observed. Dyspareunia was also significantly less frequent and increased libido was experienced. It was concluded that abdominal hysterectomy does not provoke adverse urinary or sexual symptoms and that it can have beneficial effects.

Adult↗
PubMed1993

Modified Burch colposuspension for stress urinary incontinence in females.

Modified Burch colposuspension was performed upon 186 women having clinically and urodynamically verified stress urinary incontinence (SUI). After two years, 91 percent of the patients were cured or markedly improved. The success rate was as much as 95 percent among the patients who underwent Burch colposuspension as a first operative treatment for incontinence. In the patients with recurrent SUI, the cure rate was 82 percent. Failures appeared mostly during the first six months. There were no significant differences in cure rates between the patients who underwent concomitant hysterectomy and those who did not. The comparison of two different suture materials, Dexon (polyglycolic acid) and Maxon (polyglyconate monofilament absorbable) did not produce any significant differences. Temporary urinary retention was the most common postoperative complaint. During the six to 12 postoperative months, 19 percent of the patients experienced urgency and 9 percent had mild voiding difficulties. After one year, 12 percent of the patients had rectocele or enterocele, or both, which were surgically corrected. We conclude that modified Burch colposuspension is a safe and effective primary surgical method for the treatment of stress urinary incontinence in women.

Adult↗
PubMed1992

Relation of dentin sensitivity to histological changes in dog teeth with exposed and stimulated dentin.

The effect of chronic exposure of dentin to the sensitivity of intradental nerves was studied in dogs. The dentin of canine and incisor teeth was exposed one week prior to the experiments in which 34 single fiber units dissected from the inferior alveolar nerve were recorded. In the teeth with acutely bared dentin 36 nerve fibers were tested. SEM of the chronically exposed dentin showed that practically no tubule apertures could be found since the surface was covered with bacteria and oral debris. This coating had to be removed by drilling and acid etching before any responses could be evoked. When compared to the teeth with acutely exposed dentin, the sensitivity of the fibers responding to drilling, probing, osmotic stimulation, and air blasts applied to the dentin was weakened in the chronic cases, in the sense that fewer units of those tested responded. However, cold evoked nerve activity only in some chronically exposed teeth, suggesting sensitization of the nerves. TEM revealed electron-dense substance in the dentinal tubules of the chronic teeth. Some of the material was evidently cellular remnants aspirated from the pulp and some of it, staining more faintly, could be extravasated plasma proteins. In the acute cases the tubules were emptier. Light microscopy showed histological injuries in the pulp-dentin border. It is concluded that the decrease in the responsiveness of the pulp nerve fibers in the chronic cases was due to the changes in the dentin.

Animals↗
PubMed1992

Effect of serotonin (5-HT) and calcitonin gene-related peptide (CGRP) on the function of intradental nerves in the dog.

Several inflammatory mediators including serotonin (5-HT) have been indicated to play a role in the sensitization of intradental nerves. In the present investigation, using the single fibre recording technique, the effect of locally applied 5-HT (1 mg/ml) and calcitonin gene-related peptide (rat CGRP 2 micrograms/microliters) on the function of intradental nerves in the dog was studied. The effect of these substances on the pulpal blood flow was also investigated to check their effective diffusion into the dental pulp. 5-HT induced a low-frequency background firing in 11 out of 30 nerve fibres. The number of fibres responding to probing, air blast and osmotic stimulation was increased significantly after 5-HT application. Three fibres responded to cold stimulation after 5-HT application; no responses were induced before. After CGRP application, a continuous low-frequency firing was induced only in 1 fibre out of 11 and 1 fibre which before did not respond to osmotic stimulation gave responses to saturated glucose. The responses to probing and air blasts were qualitatively unchanged. Local application of either of the substances induced a change in pulpal blood flow. It is suggested that while 5-HT is able to sensitize intradental nerves to various hydrodynamic stimuli, CGRP seems to be less effective. Pulpal inflammation with the release of inflammatory mediators may significantly affect the degree of dentine sensitivity.

Animals↗
PubMed1992

Neurophysiological mechanisms of dentin hypersensitivity.

In hypersensitive teeth pain is typically induced by cold and hot fluids or foods brought to contact with the sensitive dentin or by osmotic and mechanical stimuli. The results of animal experiments indicate that intradental A-type nerve fibres are responsible for the sensitivity of dentin. They are most probably activated by the hydrodynamic mechanism. Thus, their activation is to a great extent dependent on the condition of dentin with either open or blocked dentinal tubules. Blocking of the tubules effectively prevents the nerve activation. Correspondingly, in human experiments, the condition of the dentinal tubules greatly affects dentin sensitivity. In clinical studies significantly more open tubules are found in sensitive compared to non-sensitive areas. However, hypersensitivity may sometimes persist despite of effective blocking of the tubules. This may indicate that some other mechanisms may operate in the nerve activation instead of, or in addition to the hydrodynamic one. Inflammation may sensitize the nerve endings to such an extent that smaller fluid shifts would be sufficient for nerve activation or, for example, thermal stimulation may activate the nerves by a direct effect. On the other hand, spontaneously occurring changes in the exposed dentin, which in many cases seem to block the tubules may reduce the responses to hydrodynamic stimulation and, thus, have an opposite effect on dentin sensitivity. The results of animal experiments indicate that functional changes of this kind may occur. These results also indicate that real dentin hypersensitivity can develop as a result of inflammation induced sensitization of the nerves in the pulp-dentin border in teeth with open dentinal tubules.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Role of intradental A- and C-type nerve fibres in dental pain mechanisms.

The arousal of the two components of pain (the first rapid or sharp pain and the second dull pain) are considered to be related to activation of A delta- and C-type nociceptive primary afferents, respectively. The same dichotomy of pain sensations may also exist in teeth, although due to the short distance between the site of stimulation and the brain the two sensations might not be as clearly separated as in stimulation of, for example, the extremities. The sensations evoked by stimulation of human teeth vary according to the type of the stimuli applied. Low-intensity electrical stimulation is able to induce non-painful (prepain) sensations. At high current intensities pain is evoked. Drilling, probing and air-drying of exposed dentin induce only pain. Most studies also indicate that thermal stimulation only induces painful sensations. The quality of dental pain can vary. Typically, dentinal stimulation of teeth with healthy pulps induces sharp pain. On the other hand intense heat stimulation can result in dull pain which radiates to a wider area of the face and jaws. This component of the stimulus-induced pain seems to share some characteristics of toothache associated with painful pulpitis. Single fibre recordings of intradental nerve activity in experimental animals have shown that in addition to A-fibres a considerable number of C-type primary afferents innervate the dental pulp. This is in accordance with the results of neuroanatomical studies, which indicate that 70-80% of pulpal axons in human, monkey, dog, and cat teeth are unmyelinated. Intradental A- and C-fibre groups seem to be functionally different and can be activated separately by certain external stimuli. Comparison of the response characteristics of the pulp nerve fibres and the sensations induced from human teeth indicate that: 1) A-fibres are responsible for the sensitivity of dentine and thus for the mediation of the sharp pain induced by dentinal stimulation, 2) Prepain sensations induced by electrical stimulation result from activation of the lowest threshold A-fibres some of which can be classified as A beta-fibres according to their conduction velocities. Comparison of the responses of the A beta- and A delta-fibres indicate that they belong to the same functional group, 3) Intradental C-fibres are activated only if the external stimuli reach the pulp proper. Their activation may contribute to the dull pain induced by intense thermal stimulation of the tooth and to that associated with pulpal inflammation.

Animals↗
PubMed1991

Effect of enalapril on plasma atrial natriuretic peptide in late recovery phase of acute myocardial infarction.

A 12 week randomised, double blind, placebo controlled study on the effect of enalapril (5-20 mg daily) on the concentration of plasma atrial natriuretic peptide level and activity of the sympathetic nervous system and renin angiotensin system was done on 27 patients who had suffered an uncomplicated acute myocardial infarction two to six months earlier. None of our patients needed drug treatment for heart failure, but their exercise capacity was markedly limited. Plasma neurohormone concentrations at baseline and after 12 weeks of treatment were also compared with those of healthy controls. Concentrations of plasma atrial natriuretic peptide concentrations remained high throughout the study in those patients on beta-blockers. Enalapril treatment had no definite effect on the concentrations of plasma atrial natriuretic peptide or other neurohormone.

Aldosterone↗
PubMed1989

Reflex responses in the digastric and tongue muscles to stimulation of intradental nerves in the cat.

Electrical stimulation of tooth pulp nerves induces the digastric jaw-opening reflex in the cat, apparently due to activation of intradental A-fibres; C-fibres do not seem to be involved. In fact, reflex responses to activation of pulpal C-fibres have not been studied. In the present experiments on anesthetized cats we recorded EMG reflex responses of the digastric and tongue muscles to stimulation of the intact tooth crown, exposed dentine, and the pulp. We used stimuli that selectively activate either A- or C-fibres of the pulp. Slow heating of the tooth and application of capsaicin into the pulp, both procedures known to excite only C-fibres in the pulp, evoked licking movements of the tongue and prolonged EMG-responses in the tongue and, less consistently, digastric muscles. Similar muscle responses were elicited by high intensity electrical current pulses applied to the tooth. At low current intensities only short-duration digastric activation (jaw-opening reflex) was induced. Similar digastric jaw-opening was also evoked by drilling and air-drying of dentine, both stimuli able to activate only intradental A-fibres. These results indicate that activation of both A- and C-type pulp nerve fibres can induce reflectory muscle activation, and further, they support the concept of afferent intradental C-fibre innervation.

Animals↗
PubMed1987

The response of dog intradental nerves to hypertonic solutions of CaCl2 and NaCl, and other stimuli, applied to exposed dentine.

Responses of single nerve units from the canine and incisor pulps of anaesthetized beagles to CaCl2 (3.5 M, 4.9 M and saturated) and NaCl (2.5 M and 4.0 M) were recorded. The sensitivity of these nerve units to drilling and probing of dentine, and to drying with air blasts, was also studied. Twenty-one out of 22 units responded immediately, either with a few spikes or, sometimes, with a 2-5 s train of impulses, to hypertonic CaCl2 when applied to superficial dentine. Deep in dentine, CaCl2 induced immediately responses in 15 out of 21 units. There were responses to hypertonic NaCl in 15 out of 19 units, but only when applied deep in dentine. This firing had a latency of 15-300 s (mean 94 s) and continued until the solution was washed away. Units sensitive to CaCl2 also responded to drilling, probing and drying. When applied to the exposed pulp, CaCl2 never induced nerve activity, but hypertonic NaCl induced responses in all units tested (n = 19); the latencies were 0-300 s (mean 34 s). The mechanism of nerve activation in response to hypertonic CaCl2 is probably hydrodynamic, and common to several other stimuli as in drilling, probing and air drying. Responses to hypertonic NaCl may have been induced by a direct excitatory effect of Na+-ions on the nerve endings or axons in the pulp-dentine border.

Animals↗