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Biomedical subjects

K Johansen

Publications and source records attributed to K Johansen.

At least 235 records · Page 13Linked to original sources
PubMed1977

Tissue metabolism and enzyme activities in the rodent Heterocephalus glaber, a poor temperature regulator.

1. Tissue oxygen uptake and enzyme activities were investigated in the naked mole rat, Heterocephalus glaber, a mammal notable for its low body temperature and metabolism and poor temperature regulating ability. 2. Q10 for O2 uptake of Heterocephalus crude liver homogenates ranged from 1.91 for the temperature interval 25-30 degrees C to 1.76 within the range 30-38 degrees C, values similar to those reported for typical homoiotherms. 3. Km pyruvate of lactate dehydrogenase in heart muscle had the same temperature dependence in the mole rat and mouse. 4. O2 uptake and cytochrome oxidase activity of skeletal muscle were higher for mole rat than mouse. The reverse was true for heart muscle. Brain and liver O2 uptake showed similar values for both species, while kidney O2 uptake was highest in the mouse. 5. Pyruvate kinase activity in heart and skeletal muscle was higher in mouse than mole rat, suggesting a greater reliance on glycolysis in the former. 6. Na+, K+ -ATPase activity of liver and kidney was 60% higher in mouse than mole rat, while brain was 30% higher in mouse. 7. The results indicate that the effects of temperature on tissue metabolism in the mole rat conform to those in typical homoiotherms. The low body temperature and O2 uptake in the mole rat find no expression in the tissue respiratory capacity.

Animals↗
PubMed1977

A family with dominantly inherited mild juvenile diabetes.

A family of 53 members is described in which mild diabetes in young, non-obese subjects is transmitted through four generations from parents to children, the ratio diabetic/non-diabetic offspring of diabetic parents being 3:2 and all affected individuals having a diabetic parent. In this family, mild juvenile diabetes thus appears to be inherited as an autosomal Mendelian dominant.

Adult↗
PubMed1977

Effects of low tissue temperature on peripheral vascular control mechanisms.

Influence of low temperatures on vascular effects produced adrenaline, noradrenaline and vasoconstrictor nerve stimulation was studied in the feet of ducks. Observations were made on isolated preparations as well as on intact ducks with one or both feet immersed in ice-water. Isolated preparations were perfused with physiological solution and information on changes in vascular resistance obtained by direct measurement of flow changes during perfusion at constant pressure or by measuring changes in perfusion pressure during perfusion at constant flow. In intact ducks changes in blood flow were recorded as changes in digital subcutaneous tissue temperature. The study revealed that in the duck foot a relatively large fraction of the resistance to blood flow is found in the arteries of the proximal part of the foot. During cooling of the foot the influence of vasoconstrictor nerve stimulation and low doses of adrenaline and noradrenaline on vascular resistance is gradually lost, and it is negligible at temperatures below 8 degrees C. At these low temperatures the blood vessels stay dilated and blood flow through the web seems to be determined by the digital arterial blood pressure.

Animals↗
PubMed1977

Blood respiratory properties of rainbow trout (Salmo gairdneri) kept in water of high CO2 tension.

1. Blood O2 transport and acid-base balance were studied at 20 degrees C in rainbow trout (Salmo gairdneri) which had been kept in water of high CO2 content (15 mmHg) for at least a week. Also the blood gas chemistry of fish rapidly entering or leaving the hypercapnic environment was studied. 2. Fish entering high CO2 water suffered a sharp decrease in blood pH which significantly reduced O2 transport by the blood, but after a few hours considerable compensation was achieved. 3. After at least a week in high CO2 water, trout showed elevated plasma bicarbonate and PCO2 levels, and a decrease in plasma chloride, while pH was about 0 - 1 pH unit below the level for control fish. Oxygen transport by the blood was marginally reduced. 4. Hypercapnic fish rapidly entering fresh water showed a sharp increase in blood pH and a decrease in blood PO2. These parameters regained normal values after a few hours but plasma bicarbonate and chloride levels took much longer to regain control concentrations. 5. Acid-base balance in hypercapnic fish is discussed with particular reference to the role of the branchial ion exchanges.

Adaptation, Physiological↗
PubMed1976

Prolonged pulseless perfusion in unanesthetized calves.

Nonpulsatile left ventricular (LV) bypass was achieved in nine alert, active calves for periods of up to two weeks using a centrifugal blood pump. Data were compared to prebypass control values and to results obtained from seven calves that underwent nonthoracotomy, retrograde LV cannulation, and pulsatile bypass for up to 35 days. Nonpulsatile flow produced an increase in heart rate of 20% (P less than .05) and an increase in aortic pressure of 10% (P less than .05). Cardiac output and systemic vascular resistance were similar in both groups for three days; thereafter, vascular resistance decreased as cardiac output progressively increased. Serum renin, lactate, and pyruvate values remained normal; creatinine clearances were not significantly different than control values, and there were no significant changes in body weight. These data indicate no untoward effects as a result of prolonged pulseless perfusion.

Anesthesia↗
PubMed1976

The excretion of insulin in urine.

The concentration of biologically active insulin was measured by the isolated fat cell method in serum and urine from healthy subjects and compared with the concentration of immunoreactive insulin. In both urine and serum the values obtained by the two methods correlated closely; In addition, there was a close correlation between the concentration of biologically active and immunoreactive insulin in urine from maturity onset diabetics. Therefore, conclusions on the excretion in the urine and the urinary clearance of insulin, which are based on measurements of immunoreactive insulin, are also valid for biologically active insulin.

Adipose Tissue↗
PubMed1976

Blood respiratory properties in the naked mole rat Heterocephalus glaber, a mammal of low body temperature.

Respiratory properties of whole blood and Hb solutions have been studied in Heterocephalus glaber, a fossorial rodent, having a low body temperature (30.0-32.0 degrees C) and poor thermoregulatory ability. For comparison similar, measurements were made on laboratory mice, Mus musculus. Whole blood showed a distinctly higher O2 affinity for Heterocephalus at both 30 and 37 degrees C.P50 values were 23.3 mm Hg and 33.0 mm Hg at 37 degrees C for Heterocephalus and Mus, respectively, while at 30 degrees CP50's were 18.8 mm Hg and 24.9 mm Hg, all values at pH (b) 7.4. deltaH values (expressive of the effect of temperature on P50) were -5.8 kcal-mol-1 for Heterocephalus and -7.5 kcal-mol-1 for Mus. The CO2 Bohr effects (omega) were -0.43 and -0.50 for Heterocephalus at 37 and 30 degrees C. Corresponding values for Mus were -0.65 and -0.56. Both species had a Hill's n-value of 2.6. Red cell concentrations of 2,3-DGP were closely similar in the species being 7.3 mmol-L-1 rbc for Heterocephalus and 7.4 mmol-L-1 rbc for Mus. Stripped Heterocephalus Hb had a very high O2 affinity, at pH 7.25, 37 degrees C,P50 was 8.0 mm Hg whereas the corresponding value for Mus was 11.3 mm Hg. Addition of DPG to stripped Hb from the two species decreased O2 affinity to the same degree. The high O2 affinity of Heterocephalus blood is viewed as a possible adaptation to its burrowing habits. Its basis is inherent to the hemoglobin molecule itself and not dependent upon cofactor influence or the temperature sensitivity of the O2-Hb binding.

Adaptation, Physiological↗
PubMed1976

Respiratory properties of blood in awake and estivating lungfish, Protopterus amphibius.

Blood respiratory properties have been studied in awake and estivating African lungfish, Protopterus amphibius. Fish had been estivating 28-30 months when blood was sampled. Hematocrit, O2 capacity and blood hemoglobin concentration increased by about 50% during estivation. Red cell Hb concentration (MCHC) was unaltered. Total blood concentration of nucleoside triphosphates (NTP) was reduced 50% in estivation. Thin-layer chromatography showed that the change in NTP resulted from a GTP/Hb (guanosine triphosphate) reduction to 20% of the value in awake fish. ATP (adenosine triphosphate) concentration remained largely unaltered. GTP/Hb changes were accompanied by marked changes in O2 affinity. The P50 value in blood from awake fish was 33 mm Hg at pH 7.5 compared to 9 mm Hg for the estivating fish. The n-value changed insignificantly. An increased Bohr effect was present in estivating fish, but its importance will depend on circulating pH in the two states. Standard bicarbonate ranged from a low of 8.6 mMol-L-1 (P plasma) at pH 7.5 in an awake fish to 49.6 mMol-L-1 (P) in an estivating fish. CO2 dissociation curves showed a variable Haldane effect having its highest value in the in vivo range of PCO2. The striking increase in O2-Hb affinity during estivation is regarded as an adaptation to a reduced alveolar O2 availability associated with estivation. Altered mechanics of pulmonary ventilation and reduced ambient O2 availability caused by the subterranean habitat may have been selection pressures for the development of the high O2 availability caused by the subterranean habitat may have been selection pressures for the development of the high O2 affinity. The mechanism behind it rests with the recorded change in erythrocytic concentration of GTP.

Adaptation, Physiological↗
PubMed1976

Physiological properties of eel haemoglobin: hypoxic acclimation, phosphate effects and multiplicity.

Unlike the whole body oxygen affinity, which adapts readily to environmental oxygen tensions, haemoglobins, prepared from normoxic- and hypoxic-accimated eels (Anguilla anguilla) show no adaptive changes in oxygenation properties or in multiplicity. Hypoxic acclimation is, howeveer, accompanied by a strong decrease in red cell nucleoside triphosphates, particularly guanosine triphospphate (GTP), which depresses oxygen affinity of the composite and component haemoglobins more strongly than does the concurring ATP. The effects of pH, temperature and salts on the oxygenation properties of the (isolated) haemoglobins are reported, discussed in relation to the varying environmetal conditions encountered by eels, and compared with data on American and Japanese eels (A. rostrata and A. juponica, respectively.

Adenosine Triphosphate↗
PubMed1975

Serum insulin and growth hormone response patterns in monozygotic twin siblings of patients with juvenile-onset diabetes.

To detect abnormalities in the secretion of insulin and growth hormone in monozygotic twin siblings of patients with juvenile-onset diabetes, their responses during oral, cortisone-primed oral, and intravenous, glucose tolerance tests and intravenous tolbutamide tests were compared to those of matched controls. The twins had higher mean serum insulin levels during all tests, but differences reached statistical significance (P less than 0.02) only in the cortisone-primed test. Growth hormone levels were higher in the twins (P less than 0.04) in the intravenous tolbutamide tolerance test. The frequency of abnormal oral glucose tolerance tests among controls, diabetic monozygotic twins and the offspring of two diabetic parents was also compared. Twins and controls had nearly the same frequency of normal tests; however, the diabetic offspring had a significantly higher (P less than 0.001) prevalence of abnormal tests. These data suggest that magnitudes of environmental and genetic factors operating in monozygotic "pre-diabetic" children of diabetic parents.

Adolescent↗
PubMed1975

The relationship between diagnostic information obtained from three tests for detecting mild diabetes mellitus.

The purpose of the study was to evaluate and compare the most commonly used criteria for the interpretation of the oral (OGTT) and intravenous (IVGTT) glucose tolerance tests and the intravenous tolbutamide test (IVTT) and to establish the criteria that give the highest degree of diagnostic agreement. The highest degree of diagnostic agreement was obtained with the following limits: a) blood glucose greater than or smaller than or equal to 120 mg/100 ml within 2 1/2 h after a 100 g OGTT together with b) a k-value of greater than or smaller than or equal to 1.05 as a limit for a 25 g IVGTT and c) a 30 min blood glucose level as percentage of fasting of greater than or smaller than or equal to 77 as limit for a 1 g IVTT. Using these criteria the three tests deemed the same subjects either diabetic or nondiabetic in about 2/3 of the cases. The best correlation between the blood glucose values of the OGTT and the k-values of the IVGTT and the 30 min values of the IVTT was obtained using the blood glucose concentrations of the last part of the OGTT. The 2 and the 3 hr values were however equal to the 2 1/2 hr values with regard to the degree of correlation with the values of the intravenous test. The results indicated that the diagnostic disagreement reported previously between the three tests may partly be due to the use of blood glucose values in the first part of the OGTT for the classification of the test and partly due to the screening limits chosen for interpretation of the three test.

Administration, Oral↗
PubMed1975

Effects of ambient PO2 on hemoglobin-oxygen affinity and red cell ATP concentrations in a benthic fish, Pleuronectes platessa.

Previous studies have demonstrated that acclimation of mammals and fish to hypoxic conditions elicits opposite responses in red cell organic phosphate levels (an increase and a decrease, respectively). This investigation focuses on the "reverse" response - when the benthic fish Pleuronectes platessa, which occurs locally under hypoxic conditions, is subjected to higher oxygen tensions. Compared to the hypoxic (PO2 =30 mm Hg) situation the ATP:Hb ratio in increased (1.1 to 1.8) and oxygen affinity is increased (i.e. P50 changed from 18 to 30 mm, at pH 7.7 and 15 degrees C) by acclimation to Po2 of 150 mm Hg. Under hyperoxic conditions (Po2 =300 mm Hg) the ATP:hemoglobin ratio and blood P50 showed a surprising decrease and returned to values comparable to those in hypoxic fish (to 1.3 and 18 mm Hg, respectively). When "stripped" of organic and inorganic ions hemoglobin solutions prepared from fish acclimated at 30 and at 150 mm Hg have the same P50 and Bohr effect values, showing that the intra-erythrocytic factor rather than changes in the hemoglobin molecules, are involved. The pure hemoglobin shows high sensitivity to ATP at physiological concentrations. There is evidence that apart from the direct helcotropic effects, ATP decreases oxygen affinity in the red cells through modification of the Donnan distribution of protons across the red cell membrane. Fish acclimated to 30 and 150 mm Hg oxygen tensions showed the same oxygen consumption rates at the same oxygen tensions.

Acclimatization↗
PubMed1975

Comparative aspects of buffering capacity in muscle.

These findings are discussed in relation to the contention that a high buffer value is linked to a high work performance. This generalization does not extend to the "white" breast muscle of chicken. Its high buffer value is in part due to a high content of the dipeptides carnosine and anserine. Additionally, a hypothesis is advanced that muscle, e.g. pigeon breast muscle, can in part regulate intracellular pH by changes in the steady state concentrations of the glycolytic and citric acid cycle acids. Notably this form of pH regulation has no inherent energy requirement.

Animals↗