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Biomedical subjects

K Johansen

Publications and source records attributed to K Johansen.

At least 127 records · Page 7Linked to original sources
PubMed1988

Ductus arteriosus in pilot whales.

The ductus arteriosus (DA), connecting the aorta with the pulmonary artery in the fetus, which normally closes up just after birth in terrestrial mammals, has been claimed not to close, but to remain open in normal, adult cetaceans, just as in the adult lungfish. We have examined the hearts from two Pilot Whales. In those we found no persisting DA, but an almost totally obliterated lumen. Blood flow through the ductus of these two whales could be excluded. Instead of an anatomical shunt mammals may use a functional pulmonary shunt. To the extent diving mammals can empty their alveoli for air at depth through reinforced bronchioli, and their very compliant thorax, they block alveolar gas exchange, and thus avoid decompression sickness, nitrogen narcosis and pulmonary squeeze.

Animals↗
PubMed1988

Evaluation of serum separator tubes as a mail transport device in primary health care.

Serum separator tubes were evaluated as a serum separator system and a mail transport device. Using conventional tubes as controls, 26 serum constituents were examined. The samples were mailed from three different general practitioners to a central laboratory. Thirteen constituents had concentrations that were significantly different from the concentration in the conventional tubes. When medically important coefficients of variations were taken into account, however, the changes of only two constituents (potassium and cobalamin) were regarded as important.

Blood Chemical Analysis↗
PubMed1987

Control of breathing in an amphibian Bufo paracnemis: effects of temperature and hypoxia.

Lung ventilation was measured in the toad, Bufo paracnemis, weight 500-800 g, at 15, 25 and 32 degree C during normoxia and hypoxia (5, 10, and 15% inspired O2). Arterial blood gases were measured during normoxic breathing. Typically breath-holds alternated with ventilatory periods, which were initiated by a stepwise pulmonary deflation. Then a series of breaths consisting of both expiratory and inspiratory volumes followed. At the end of the period the lungs were inflated in several steps. Increased temperature markedly augmented ventilation mostly through a five-fold increase in the number of ventilatory periods per unit time. Ventilation was also enhanced by hypoxia and this response was greatest at the highest temperature. Arterial PO2 rose from 35 to 96 Torr when temperature increased from 15 to 32 degrees C. Bufo resembles reptiles regarding these responses.

Animals↗
PubMed1987

Effects of graded exercise on blood gas tensions and acid-base characteristics of rainbow trout.

A swim tunnel respirometer and an extracorporeal blood circulation technique allowed continuous collection of data from exercising fish below and near their critical speed. Swimming at speeds below maximum showed no changes in plasma Na+, Cl- and lactate concentrations but increased levels of blood hemoglobin and plasma K+. PaO2 and PaCO2 showed an exponential decrease and increase respectively and related to swimming speed. Increased swimming speed changed the acid-base status toward a mixed respiratory and metabolic acidosis. Upon reaching maximum speed sudden and large increases in plasma Na+, K+ and lactate concentrations occurred associated with a large metabolic acidosis.

Acid-Base Equilibrium↗
PubMed1987

Blood flow uphill and downhill: does a siphon facilitate circulation above the heart?

1. Despite the continuity of the circulatory system, blood flowing down the veins of the neck does not assist blood flowing up the arteries. Because of collapsible veins, gravitational pressure gradients are not matched in arterial and venous sides of circulatory loops above the heart as would be necessary for a siphon to operate. 2. All animals have arterial blood pressures capable of lifting the blood to the head without the assistance from a siphon. In cases of longer vertical distances, such as in giraffes and climbing snakes, the heart does more work against the effects of gravity on the arterial blood column. 3. The potential energy of the blood in the head is lost as frictional heat produced in the veins.

Animals↗
PubMed1987

Comparative model analysis of central shunts in vertebrate cardiovascular systems.

The incomplete double circulation of air-breathing fishes and lungfishes, amphibians, reptiles and embryonic birds and mammals has been analyzed using a simplified mode comprising the intra- and extracardiac shunts and compartments for the gas exchange (gills, lungs, skin, etc.) as well as systemic tissue gas exchange. The intracardiac shunting is defined and given common symbols for all species of animals analyzed. Two types of equations, fluid-flow and mass-flow equations, are derived for each model, which are solved to give shunting rate as a function of blood O2 content of the principal cardiac compartments and vessels. The model analysis not only offers possibility for an overall average evaluation of central shunts, but also suggests which blood samples must be determined for evaluation of the shunt patterns.

Animals↗
PubMed1987

Respiratory modulation of shivering intensity in the pigeon.

Respiration and shivering were measured in unanaesthetized, cold-exposed pigeons using pneumotachography and electromyography, respectively. The instantaneous intensity of shivering in the pectoral muscle varied in phase with respiration. Power spectral analysis showed that the main frequency components of respiration and demodulated EMG coincided exactly. The intensity of shivering was highest during end-expiration and lowest at end-inspiration. This was confirmed by cross-correlation analysis of respiration and demodulated EMG. The absolute level of modulation remained constant (c. 10 microV peak-to-peak) despite changes in the general intensity of shivering. On the other hand, the relative depth of modulation was highest during incipient shivering. These facts indicate that only a part of the motor units recruited for shivering is susceptible to respiratory modulation and that this part is first recruited during incipient shivering. Inhalation of 5% CO2 did not affect the interaction between respiration and shivering although respiration frequency varied from 25 to 60 min-1. Thus, pulmonary chemoreceptors do not mediate this effect. It is suggested that the interaction between respiration and shivering occurs directly in the CNS. The question whether the interaction is adaptive for the animal or merely reflects a common evolutionary history of the underlying neural circuits is discussed.

Animals↗
PubMed1987

The objective diagnosis of vibration-induced vascular injury.

For 44 patients with vibration-induced white finger and a reference group of 25 healthy men, finger systolic blood pressure (FSBP) before and after local cooling, skin temperature, and rewarming rates were determined before and after vasodilation (body warming and alcohol). An estimation of the proportions of vasopasm and organic changes was possible, and cutaneous changes could be separated from changes in the main digital vessels. The arm blood pressure was higher for the patients and the fingertip temperatures were lower, but both normalized after vasodilation. The FSBP values were equal in the two groups before local cooling. Afterward the patients had lower FSBP values which remained unchanged after the postvasodilatation cooling. Ten patients, all smokers, reacted with complete arterial closure after local cooling. When this group was separated from the other smoking patients, there was no significant difference between the smoking and nonsmoking patients, and the FSBP differences between the patients and referents was almost eliminated. It was concluded that, in vibration-exposed patients, injuries to skin circulation seem to be more frequent than injuries to the main digital vessels, except for some smokers, who have severe vasopasm combined with organic changes.

Adult↗
PubMed1986

Familial tendency for abdominal aortic aneurysms.

To examine the hypothesis that a tendency toward aneurysmal degeneration of the abdominal aorta may be inherited, we compared the family histories of 250 patients with abdominal aortic aneurysm (AAA) with those of 250 control subjects. Among the control subjects, six (2.4%) reported having a first-degree relative with an aneurysm, compared with 48 (19.2%) of the patients with AAA. After adjustment for age and sex, this corresponds to an estimated 11.6-fold increase in AAA risk among persons with an affected first-degree relative. This study suggests that the relatives of patients with AAA may themselves be at significantly increased risk for the development of aneurysmal degeneration. Because early diagnosis and elective management of AAA significantly prolong life, noninvasive screening to detect early AAA formation may be warranted in relatives of patients with AAA.

Aged↗
PubMed1986

Diabetes mellitus, atherosclerosis, and the 5' flanking polymorphism of the human insulin gene.

On the 5' side of the human insulin gene is a highly polymorphic locus containing 2 major size classes of DNA restriction fragments which segregate in families as stable genetic elements. Fragments with an average size of about 600 base-pairs (bp) (the 'L-allele') seem to be a weak genetic marker for type 1 (insulin-dependent) diabetes mellitus, whereas fragments of an average size of about 2500 bp (the 'U-allele') have hitherto been associated with type 2 (non-insulin-dependent) diabetes mellitus and diabetic hypertriglyceridaemia. Recent evidence does not confirm the association between the U-allele and type 2 diabetes. Our own studies suggest that the U-allele is a fairly strong marker for the development of atherosclerosis with a relative risk for U-carriers of 3.36. The U-allele has not been associated with conventional cardiovascular risk factors such as body weight, blood pressure, or levels of blood glucose, triglycerides or lipoproteins. The putative functions of the polymorphic region in the aetiology of type 1 diabetes and atherosclerosis, and the relation of this region to other genetic markers for these disorders are not known.

Alleles↗
PubMed1986

Aortoenteric fistula. A 7 year urban experience.

In this 7 year review of the operative records of a single city's teaching hospitals, we found 28 patients with aortoenteric fistulas. Among 25 patients with secondary aortoenteric fistulas, 80 percent presented with a herald bleed. Sepsis was rare. Most diagnostic maneuvers, with the possible exception of upper gastrointestinal tract endoscopy, computerized axial tomography, or ultrasonography, were unhelpful. As noted by others, graft excision, aortic ligature, and extraanatomic bypass is the only predictably useful operative therapy. Initial hospital survival was 60 percent, but this decreased to 36 percent because recurrent aortic complications developed in more than half the initial survivors, 75 percent of whom died. Although the pathogenesis of aortoenteric fistulas remains obscure, our study demonstrates that patients who have previously undergone complicated, repeated, or emergency aortic operations, including previous repair of an aortoenteric fistula, are at high risk for the development of another aortoenteric fistula. Serial screening by noninvasive imaging techniques, such as ultrasonography or computerized axial tomography, may be warranted in these patients.

Aged↗
PubMed1986

Autonomic nervous control of the circulatory system in the air-breathing fish Channa argus.

The control of the cardiovascular system with particular emphasis on the regulation of blood distribution in the gills and air-breathing organ was studied in the air-breathing teleost Channa argus. Perfused head preparations were used in addition to experiments with isolated strip preparations of arteries and heart chambers. The distribution of adrenergic nerves was investigated using Falck-Hillarp fluorescence histochemistry. This preliminary study shows an adrenergic control system composed of chromaffin cells and adrenergic nerves similar to that found in other teleosts investigated, although the systemic arteries (coeliac artery, dorsal aorta and the vasculature of the air-breathing organ) appear to lack an adrenergic innervation. The reactions of isolated artery strip preparations to acetylcholine and adrenaline resemble those seen in other teleosts, and there is a prominent inhibitory effect of L-isoprenaline suggestive of arterial beta-adrenoceptors. The general vascular resistance of the gill apparatus-air-breathing organ increases in response to acetylcholine or adrenaline, and there is a redistribution of perfusion flow from the air-breathing organ circuit (anterior venous outflow from the first and second pair of gills and the air-breathing organ) to the general systemic circuit (dorsal aortic outflow from the third and fourth pair of gills). Stimulation of the vagal branch entering the air-breathing organ mimics the effects of acetylcholine or adrenaline. This innervation is probably non-adrenergic since no adrenergic nerve fibres could be demonstrated in the vasculature of the air-breathing organ using the histochemical technique. An adrenergic control of the vasculature of the air-breathing organ is not likely, since the concentration of adrenaline needed to affect the vasculature is not reached in the plasma even during "stress".

Acetylcholine↗
PubMed1986

Nonresective therapy for aortic aneurysm: results of a survey.

We reviewed the experience of 120 vascular surgeons with nonresective therapy for abdominal aortic aneurysm (AAA) in medically unstable patients. Of a total pool of 206 patients, 88 underwent iliac artery ligation, which was combined with angiographic attempts at intrasaccular thrombosis in 80% of cases. The remaining 118 patients had ligation of the aneurysm proximally and distally. In all cases distal perfusion was restored, usually by axillofemoral bypass. Our study demonstrated a significantly higher risk of postoperative AAA rupture (20% vs. 3.3%, p less than 0.0001) and death (34% vs. 5.1%, p less than 0.000001) among patients treated by ligation distal to the AAA alone, whether intrasaccular thrombosis occurred or not. These results support the contention that if nonresective therapy is chosen for the occasional patient deemed too ill to undergo standard AAA resection, AAA exclusion by proximal and distal ligation should be performed.

Aorta, Abdominal↗
PubMed1986

Enteral versus parenteral nutritional support following laparotomy for trauma: a randomized prospective trial.

Although enteral nutrition is considered more 'physiologic' than parenteral nutrition, there is greater published experience with parenteral nutrition in trauma patients. To compare the efficacy of these two techniques, we prospectively randomized multiple trauma patients during their admission laparotomy to receive either central venous parenteral nutritional (TPN: n = 23) or enteral nutrition by jejunostomy (Jej: n = 23). Nutritional support began on the first postoperative day; the study period continued a maximum of 14 days. There were no significant differences between the two groups in age, sex, injury severity, estimated caloric needs (3,322 TPN; 3,114 Jej), hours to achieve full prescription (77 PTN; 79 Jej), or the number of days on nutritional support (22 TPN; 25 Jej). Average daily caloric intakes, nitrogen balance results, and complication rates were also comparable. These results suggest that early postoperative jejunostomy feeding is a safe and efficacious choice for multiple trauma patients undergoing laparotomy.

Adult↗
PubMed1986

Detection of nocturnal hypoglycemia in insulin-treated diabetics by a skin temperature--skin conductance meter.

The efficacy and credibility of a skin temperature--skin conductance meter (Teledyne Sleep Sentry) for detecting hypoglycemia was studied during night-time in 22 adult insulin-treated diabetics. Capillary blood glucose concentration was measured 99 times (when the alarm sounded, in case of hypoglycemic symptoms, and at 3 a.m.). Hypoglycemia was defined as a capillary blood glucose concentration of less than or equal to 3 mmol/l. Blood glucose was measured 61 times in connection with sounding of the alarm and 38 times without the alarm sounding. At 3 a.m. the Sleep Sentry sounded the alarm 22 times, of which hypoglycemia was present 6 times giving a diagnostical specificity or diagnostical true positive rate of 0.27 (95% confidence limits 0.11-0.50). In 35 of 38 cases of no alarm the blood glucose was greater than 3 mmol/l, giving a diagnostical sensitivity of 0.92 (95% confidence limits 0.79-0.98). The Sleep Sentry sounded the alarm in 6 of 9 cases of hypoglycemia, giving a nosological sensitivity of 0.67 (95% confidence limits 0.30-0.93). The Sleep Sentry did not sound the alarm in 35 of 51 cases of non-hypoglycemia, giving a nosological specificity of 0.69 (95% confidence limits 0.54-0.81). In other words, the Sleep Sentry detects about 2/3 of blood glucose values less than or equal to 3 mmol/l, but in addition it sounds a false alarm in 2/3 of the cases.

Adolescent↗