The nuclear envelope has a relatively small volume, but is connected up to the vastly larger endoplasmic reticulum. The Ca2+ concentration in the lumen of the interconnected nuclear envelope and endoplasmic reticulum network is in the resting state maintained at a level of more than 100 microM. There are specific Ca2+ release channels present in the inner nuclear membrane that can be activated by inositol trisphosphate or cADP ribose. The system, therefore, allows selective release of Ca2+ into the nucleoplasm which could be important for the control of specific types of gene expression.

Animals↗

PubMedDate not supplied

Validity of microsphere model in cerebral blood flow measurement using N-isopropyl-p-(I-123) iodoamphetamine.

A microsphere model is sometimes used when calculating cerebral blood flow (CBF) using N-isopropyl-p-[I-123]iodoamphetamine (IMP), and is based on the assumption that there is essentially no washout of IMP. The validity of a microsphere model was investigated by comparison with the values of CBF obtained by means of a model which takes into consideration the diffusion of IMP from brain tissue to blood (nonmicrosphere model). When calculating CBF by the latter model, the look-up table method was used with expression of the double integral in the model equation by the recursion relations, a method which is useful for obtaining pixel-by-pixel values. The average rate constants for diffusion from brain to blood of gray and white matter were 0.021 and 0.0016 min-1, respectively. The values of CBF obtained by applying a microsphere model to the data acquired from 0 to 3.2 min after IMP injection were overestimated by approximately 23% compared with those values obtained using a nonmicrosphere model. This is considered to be due to the effect of the IMP activity in the vascular space. Values obtained using the data acquired from 3.2 to 6.4 min were underestimated by approximately 15%. When the values of CBF obtained by a microsphere model were interpolated, they became nearly equal to those obtained using a nonmicrosphere model at about 4 to 5 min after injection. This is suggested to be the reason why the underestimation due to diffusion from brain to blood is cancelled out by the overestimation due to the IMP in the vascular space. Our preliminary results suggest that it is necessary to take the diffusion of IMP from brain tissue to blood into account for the quantification of CBF using IMP.

Amphetamines↗

PubMedDate not supplied

Detection of the B waves in the oscillation of intracranial pressure by fast Fourier transform.

Intracranial pressure (ICP) oscillation consists of a cardiac-induced component, a respiration-induced component and fluctuation of the base level of ICP. Lundberg reported three types of fluctuations of the base level of ICP with increasing ICP which were referred to as A, B and C waves. Computer algorithms for sampling, processing and displaying ICP data were investigated to depict the power spectrum of ICP oscillations by fast Fourier transform (FFT), thus enabling the B wave to be automatically detected. A power peak was found in the ICP power spectrum between 30 and 120 s, which corresponds to the frequency of the B wave. The maximum power, corresponding to the B-wave amplitude was above 0 dB. An appropriate sampling interval for FFT inputs was about 8 s for real-time processing of the ICP data. The mean ICP value was found useful for making the B-wave peak clearer by reducing the cardiac and respiratory components of ICP oscillations; the window function had no effect on B-wave detection in the ICP power spectrum.

Algorithms↗

PubMedDate not supplied

Hypogonadism of male prolactinomas: relation to pulsatile secretion of LH.

In order to investigate whether a hypothalamic disorder cause hypogonadism in male prolactinomas, LH pulsatile secretion was studied in 13 male patients. Serum PRL levels ranged from 186 to 45,000 ng ml-1 before treatment, and all the tumors were macroadenomas. Reduced LH secretion was revealed in 5 of 13 patients, and FSH was reduced in 1 of 13. Serum testosterone (T) levels were lower than the normal limit in all the patients. HCG tests in 3 patients showed good responses, but the peak values of T were lower than those of normal men. LH pulsatilities were examined in 5 hyperprolactinemic patients before treatment, in 4 hyperprolactinemic patients after operation, and in 8 normoprolactinemic patients after operation and/or bromocriptine treatment. There was no significant difference of the mean LH values, the frequencies of LH pulses, and amplitudes among the hyperprolactinemic patients before operation (n = 5), the normoprolactinemic patients after operation (n = 8), and normal men (n = 7). From these results, it was evident that the hypothalamus and pituitary function of male prolactinomas were well preserved, in spite of higher serum PRL levels and larger tumor size than those reported in females. It is suggested that the main cause of hypogonadism in these patients is due to testicular dysfunction resulting from excessive serum PRL.

Adult↗

PubMedDate not supplied

Antitumor effect of bromocriptine on estrogen-induced rat prolactinomas: ultrastructural alterations of secretory granules.

A quantitative analysis of ultrastructural alterations of secretory granules in correlation with prolactin (PRL) concentrations in estrogen-induced rat prolactinomas was performed to investigate the mechanism of the cytosuppressive action of bromocriptine (CB). The secretory granules of CB-treated adenomas increased in number but not in volume. The degree of exocytosis of the granules showed no significant decrease as reported previously, but rather an increase in adenomas treated with CB for 3 days. Radioimmunoassay revealed a decrease in PRL concentrations of adenoma tissues. and a marked reduction in serum PRL levels. These results suggest a low level of PRL in the secretory granules of the CB-treated pituitary adenomas.

Adenoma↗

PubMedDate not supplied

Scintigraphic study on the distribution of radiolabeled cis-diamminedichloroplatinum (II) in the tumor-bearing rabbit: a comparison between intra-arterial injection with lipiodol and intravenous injection.

To compare the distribution of cis-diamminedichloroplatinum (II) (CDDP) on scintigraphic images between intra-arterial injection with lipiodol and intravenous injection, we obtained serial scintigraphic images using radiolabeled CDDP (Pt-195m CDDP), which had a high specific activity (7.4 x 10(6) Bq [200 microCi]/mg-CDDP), in the rabbit VX-2 tumor system. A dose of 9.25 x 10(6) Bq (250 microCi) of Pt-195m CDDP was injected at one shot via an ear vein, while 7.4 x 10(6) Bq (200 microCi of Pt-195m CDDP mixed with 1 ml of lipiodol was injected at one shot via a saphenous artery. Mean pixel count, which was corrected for the total dose injected, in the arterially injected tumor always exceeded than that in the intravenously injected tumor. Pt-195m CDDP uptake by the rabbit tumor at 2 hr was 7.8% of the total injected dose with intravenous injection and 16.0% with intra-arterial injection. These data suggest that intra-arterial injection with lipiodol is a more useful method to increase CDDP uptake by tumors than intra-venous injection.

Animals↗

PubMedDate not supplied

Distribution of radiolabeled cis-diamminedichloroplatinum (II) on scintigraphic images in the tumor-bearing rabbit.

To evaluate the feasibility of using scintigraphic images to assess the distribution of cis-diamminedichloroplatinum (II) (CDDP), we obtained serial scintigraphic images using radiolabeled CDDP (Pt-195m CDDP), which had high specific activity (7.4 x 10(6) Bq [200 microCi]/mg-CDDP) in the rabbit VX-2 tumor system. Radioactivity at the heart decreased in a biexponential manner, with an initial half-time of 15.3 min and secondary phase of 4.5 days. Time-activity curves revealed that the tumor/heart ratio was greater than 1.0 (1.0-1.1) between 30 min and 4 hr after intravenous injection. The scintigraphic study clearly depicted the tumor. Pt-195m CDDP uptake by the rabbit tumor at 2 hr was 7.8% of the total injected dose. These data suggest that scintigraphic imaging using Pt-195m CDDP is a promising method for imaging tumors and evaluating their CDDP uptake.

Animals↗