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J T Hansen

Publications and source records attributed to J T Hansen.

At least 73 records · Page 4Linked to original sources
PubMed1982

Ultrastructure of rat pinealocytes during the last phase of pregnancy.

The numbers of Golgi profiles, dense-core vesicles, vacuoles containing a flocculent material, lysosomes, lipid droplets, 'synaptic' ribbons and microtubular sheaves were counted in the rat pinealocytes in the last 5 days of pregnancy. The numbers of Golgi profiles and dense-core vesicles increase at days 21 and 22, while numbers of LYS and LD increase the day before parturition. On the contrary, the number of VFC decreases in the final day of pregnancy. The results of the present study suggest that the pineal gland may play a subtle role in pregnancy.

Animals↗
PubMed1982

Quantitative changes in the numbers of dense-core vesicles and 'synaptic' ribbons in pinealocytes of the Djungarian hamster (Phodopus sungorus) following sympathectomy.

The dense-core vesicles and 'synaptic' ribbons were counted in Djungarian hamster pinealocytes after superior cervical ganglionectomy. Sympathectomy caused a decrease in the number of dense-core vesicles in pinealocytes, suggesting diminished secretory activity of these cells. An increase in the number of 'synaptic' ribbons after superior cervical ganglionectomy supports the hypothesis that adrenergic innervation of the pineal gland influences the level of 'synaptic' ribbon formation.

Animals↗
PubMed1981

Morphological aspects of secretion in the glomus cell paraneurons of the carotid body: evidence for calcium-dependent exocytosis.

Carotid bodies were studied using thin section and freeze-fracture preparations following incubation in physiological media. Glomus cells incubated in medium containing either no calcium (Ca2+), 1.1 mM Ca2+, or 19 microM ionophore A23187 alone appeared normal with no evidence of exocytosis. However, cells incubated in the presence of Ca2+ and A23187 exhibited exocytosis, and a significant (P less than 0.01) decrease in the number of catecholamine-containing dense-core vesicles per micron2 of cytoplasm. Numerous dense-core vesicles were observed aligned along the glomus cell plasma membrane, and vesicles in close apposition to the membrane exhibited an electron-dense connecting material between the vesicle and the plasma membranes. Freeze-fracture replicas of the P-face of the glomus cell plasma membrane showed numerous 40-60 nm pits indicative of fusion sites between the vesicle and the plasma membranes. These results suggested that vesicle exocytosis was Ca2+-dependent and not restricted to specific active zones on the plasma membrane adjacent to afferent nerve endings. Therefore, catecholamine secretion and neuromodulation by these paraneurons may also occur by a mechanism of paracrine secretion.

Animals↗
PubMed1980

Early ultrastructural changes in the myocardium following thyroxine-induced hypertrophy.

The model of myocardial hypertrophy induced by thyroxine was studied with particular regard to the early ultrastructural changes in fractional volume of the mitochondria and myofibrils, and capillary distribution. Following injections of L-thyroxine (25 mg/kg IP) for 9 consecutive days, rats were sacrificed by vascular perfusion and cardiac tissue samples from the mid-wall zone of the left ventricle were processed routinely for electron microscopy. Heart weight/body weight ratios of thyroxine treated (T) rats showed a significant increase (P less than 0.001) over the ratios in control (C) rats. Likewise, the fractional volume of mitochondria (42%) was significantly increased (P less than 0.001) in the myocardium of T rats when compared with C rats (31%). However, the fractional volume of myofibrils was significantly decreased in the myocardium of T rats (P less than 0.001) and there was no significant difference between the hearts of T and C rats with respect to capillary luminal area/myocyte area. The mitochondria/myofibril ratio was increased in the hearts of T rats (0.82) over that found in control hearts (0.52). These results suggest that in the early stages of thyroxine-induced myocardial hypertrophy there is not an immediate increase in capillary area which may account for the ischemia and significant increase in mitochondrial volume which characterized myocardial hypertrophy in this model.

Animals↗
PubMed1979

Calcium binding sites in the vesicles of the carotid and aortic body chief cells.

Chief cells of the carotid and aortic body chemoreceptors possess numerous cytoplasmic dense-core vesicles which are known to contain primarily dopamine. Following fixation in solutions containing 50 mM CaCl2, a 20--30 nm electron-dense particle (EDP) is often observed eccentrically located in many of the vesicles. Approximately 44% of the carotid body and 16% of the aortic body vesicles contain an EDP. The EDP probably represents the Ca++ binding site critical to the stimulus-secretion coupling events culminating in exocytosis of these vesicles. The presence of Ca++ in the cytoplasmic vesicles was verified by electron probe X-ray microanalysis.

Animals↗
PubMed1979

An ultrastructural stereological analysis of the aortic body chief cell of adult rabbits.

The chief cells of the aortic body (subclavian body) of adult New Zealand white rabbits were examined by ultrastructural stereological analysis. The chief cell nuclei occupy 26.5% of the total volume. Dense-core vesicles account for 16.5% of the cytoplasmic volume, followed by mitochondria (11.6%), endoplasmic reticulum (3.3%), and Golgi apparatus (0.6%). The dense-core vesicles measure approximately 131.6 nm in diameter (corrected) and exhibit a heterogeneous size distribution. Both perivascular adrenergic nerve terminals and presumptive afferent terminals presynaptic to the chief cells are observed. The mean synaptic vesicle size of the terminals adjacent to chief cells is 54 nm. The heterogeneous size distribution of the dense-core vesicles of chief cells may indicate the storage of different biogenic amines and/or different secretion or maturation states within the chief cells.

Animals↗
PubMed1979

The pineal gland of the gerbil, Meriones unguiculatus. III. Morphometric analysis and fluorescence histochemistry in the intact and sympathetically denervated pineal gland.

Morphometric analytical procedures were employed to study the pineal gland of the Mongolian gerbil following superior cervical ganglionectomy (SCGX). The purpose of this study was to define the effects of sympathetic denervation on the morphology of the gland at two time periods, 0500 and 1900 h (one hour before lights-on and lights-off, respectively). Fluorescence histochemistry was employed to determine catecholamine and indoleamine content in intact and denervated pineal glands. After SCGX, the pinealocytes decrease in size, concretions are prevented from forming, and the yellow fluorescence in the gland is lost. Following denervation a depression in the volume of most of the pinealocyte organelles, i.e., SER, RER/ribosomes, free cytoplasm, mitochondria and presumptive secretory vesicles, was also observed. However, synaptic ribbons increased in volume in the gerbils that had been killed at 1900 h. It appears that the sympathetic innervation to the pineal gland is a requirement for the presumptive secretory activity of the pinealocytes.

Animals↗
PubMed1979

Effect of althesin anesthesia on blood loss during therapeutic abortion. A comparison with local and thiopental anesthesia.

During recent years, the use of steroid anesthesia has rapidly increased. In our hospital, a number of surgical procedures have been performed under Althesin anesthesia, and in some cases the peroperative bleeding seemed to be rather profuse. Blood loss was studied in 90 healthy women in the first trimester of pregnancy undergoing therapeutic abortion using different types of anesthesia. The patients were divided into three equal groups according to the duration of pregnancy. In each group, 10 patients underwent operation under local anesthesia, 10 under thiopental anesthesia and 10 under Althesin. In all three groups, blood loss was the smallest when local anesthesia was used (Fig 1). Amounting to only one third to one half of that occurring under thiopental anesthesia. Under thiopental anesthesia the blood loss gradually increased with increasing gestational age with moderate variations. Alternatively, in this investigation, Althesin anesthesia was characterized by pronounced blood loss, particularly in the ninth and tenth weeks of pregnancy, and in some cases by rather profuse bleeding. We find that Althesin anesthesia should be used for gynecological surgery only in departments which are equipped to control profuse bleeding and possible cardiovascular complications.

Abortion, Therapeutic↗
PubMed1978

Time course of the disappearance of pineal noradrenaline following superior cervical ganglionectomy.

Pineal glands were collected from superior cervical ganglionectomized (SCGX) and sham-treated rats at time intervals following surgical manipulation. Pineal noradrenaline (NA) levels were quantitated by a radioisotopic-enzyme technique, or the pineals were examined by histofluorescence or electron microscopic techniques. A significant decline in pineal NA content was observed by 12 hours with a virtual disappearance of NA by 24 hours following SCGX. The depletion of NA content correlated with the disappearance of synaptic vesicles and the appearance of generalized fine structural degeneration of the sympathetic nerve endings in the pineals. Then results indicate that less than one day is required to remove all of the potentially, functional neurotransmitter from the denervated pineal gland. These observations agree closely with the time course of degeneration of other sympathetic nerve terminals following SCGX.

Animals↗
PubMed1978

Development of type I cells of the rabbit subclavian glomera (aortic bodies): a light, fluorescence and electron microscopic study.

The embryogenesis of the subclavian glomera (aortic bodies) is controversial. Past investigators have attributed the development of the Type I cells to mesodermal and/or neural elements. Based on the results of the present light microscopic, fluorescence histochemical and electron microscopic study of rabbit aortic bodies from 16 days of gestation (term:31 days) to four days postpartum, it appears that the Type I glomus cell are derived from cells of neural crest origin. The subclavian anlage is associated with cells of neural crest origin. The subclavian glomus anlage is associated with cells of vagal origin throughout its development. Evidence of Type I cell development from pre-existing mesodermal condensations is not observed. Type I cells exhibit formaldehyde-induced-fluorescence by the twentieth day of gestation. Dense-cored cytoplasmic vesicles are apparent by the sixteenth day of gestation. The number of cytoplasmic vesicles increases steadily, but the greatest increase of vesicles is observed between the twenty-eighth day of gestation and birth. Primitive Type I glomus cells exhibit abundant polysomes and rough endoplasmic reticulum indicative of synthetic activity. Nerve terminals are apparent adjacent to Type I cells by the twentieth day of gestation, but synaptogenesis does not occur until sometime between the twenty-fourth and twenty-eighth days of gestation. Abundant vascularity, characteristic of chemosensory glomera, is not achieved until the twenty-eighth day of gestation.

Animals↗
PubMed1978

Therapeutic abortion in an out-patient clinic. A prospective investigation of complications and patient acceptability.

The incidence of complications associated with therapeutic termination of pregnancy was analysed in 1349 patients, whose average age was 26.3 years. Of the patients, 51.8% were 25 years or under; 56.3% were seen in or before the 8th week of pregnancy, and 17.4% had previously had one or more legal abortions. All the operations were performed under local anaesthesia and by the same doctor, who was an experienced gynaecologist. Complications associated with the operation occurred in 14 patients (1%), viz. infections in the uterus and tubes, 9 cases; incomplete abortion necessitating repeat curettage, 4 cases; and profuse bleeding requiring blood transfusion, 1 case. No uterine perforations or cervical ruptures were encountered. Questioned about subjective discomforts of the opeation, 7.4% of the women answered that the discomfort had been considerable, whereas 62.6% described it as only slight; 4.8% would have perferred general anaesthesia. We conclude that therapeutic abortion can be performed safely and with an acceptably low incidence of complications in out-patients, provided the operations are performed by an experienced gynaecologist.

Abortion, Therapeutic↗
PubMed1977

Morphometric study of the aortic body type I cell.

The subclavian glomus (aortic body) of New Zealand white rabbits was examined ultrastructurally using stereological morphometric analysis. The Type I cells of the glomus possess numerous electron-opaque vesicles which occupy approximately 12% of the cytoplasmic volume of the cells. The amine-containing vesicles comprise a heterogeneous population of vesicles with a mean caliper diameter of 113.5 nm. Differences in vesicle diameters may indicate the storage of different biogenic amines, different secretion or maturation states between glomera and/or additional physiological functions for the glomera.

Animals↗
PubMed1977

Freeze-fracture study of the carotid body.

Replicas of freeze-fractured rat carotid body chief (Type I) cells reveal the normal complement of cytoplasmic organelles. En face fractures of the chief cell plasmalemma exhibit occasional sites of fusion of the amine-containing vesicles which characterize the carotid body. The endothelial cells lining the capillary network of the carotid body display numerous pinocytotic vesicles often oriented in linear arrays, and occasional fenestrae. The endothelial cells are joined together by tight junctions which appear as grooves (B face) forming a continuous network over the membrane.

Animals↗