Overcoming MDR by ultrasound-induced hyperthermia and P-glycoprotein modulation

We assessed the effects of combining ultrasound-induced hyperthermia (USHT) with the P-glycoprotein modulator PSC 833 on cellular retention and cytotoxicity of rhodamine 123 (R123) and doxorubicin in the parent and multidrug resistance (MDR) variants of two human cancer lines. USHT significantly increased cellular uptake of R123 and doxorubicin. Without PSC 833, release of R123 and doxorubicin from both USHT-treated and untreated cells was rapid. As expected, PSC 833 (0.5 microM) only slowed their release into the MDR lines. Interestingly, despite the differences in their starting amounts, PSC 833 was effective in prolonging R123 and doxorubicin release from both USHT-treated and untreated MDR cells. PSC 833 did not augment the cytotoxicity of doxorubicin in parent lines but did cause a significant increase in cytotoxicity of doxorubicin in the MDR lines. However, the combined effect of USHT and PSC 833 on cytotoxicity of doxorubicin far exceeded that produced by USHT or PSC 833 alone.

Transdural spinal cord herniation: imaging and clinical spectra

PURPOSE

Transdural herniation of the spinal cord is a rarely reported clinical entity, and many of the existing reports were published before the advent of MR imaging. We describe five current cases and compare them with findings in 25 cases reported in the literature to delineate the clinical and imaging spectra of transdural spinal cord herniation.

METHODS

MR imaging, CT myelography, and conventional myelography were performed in five patients with transdural herniation of the spinal cord. These studies, along with clinical findings, are described. Intraoperative photographs are included for one case. The salient features of both the current and previously reported cases are summarized in tabular form.

RESULTS

In three cases, transdural spinal cord herniation occurred posttraumatically, in one case the cause was iatrogenic and in the others the herniation occurred spontaneously. Imaging features not previously reported include dorsally directed herniations at thoracolumbar levels (two patients), apparent (lacking surgical confirmation) syringomeyelia (one case), a vertebral body nuclear trail sign (one case), and intramedullary hyperintensities on MR images (two cases). Clinical features not previously reported include unilateral pyramidal-sensory deficits (one case) and isolated unilateral pyramidal signs (one case). Clinical findings similar to previous reports include progressive paraparesis (two cases) and progressive Brown-Séquard syndrome (one case).

CONCLUSION

Our five cases illustrate certain clinical and imaging findings not previously reported, and, together with the established features of the 25 cases in the literature, delineate the spectra of transdural spinal cord herniation.

Pulsatile prolactin secretion in hyperprolactinemia due to presumed pituitary stalk interruption

PRL, like other anterior pituitary hormones, is normally secreted in a pulsatile fashion. However, it is not known whether such pulses depend on dopamine and/or other hypothalamic factors. This question can be addressed by investigating patients with large pituitary mass lesions, since such patients often have hyperprolactinemia due to disruption of normal hypothalamic input to the pituitary gland. Six such patients (5 with non-PRL-secreting tumors and 1 with a craniopharyngioma) and 11 healthy control subjects had PRL levels measured every 15 min over 24 h. PRL pulses were located by cluster analysis. All patients had PRL pulses of normal frequency, but increased amplitude. Circadian variation in PRL pulse amplitude, present in healthy women, was abolished in tumor patients. These results imply that normal pituitary levels of dopamine do not control the generation of PRL pulses. Instead, PRL pulses may arise from the pituitary gland, with pulse amplitude and circadian rhythm modulation by dopamine and other hypothalamic factors. Alternatively, the mild hyperprolactinemia associated with large hypothalamic-pituitary tumors may represent partial impairment of dopamine secretion, with sufficient pituitary dopamine levels to maintain normal PRL pulse frequency.

Pulsatile glycoprotein hormone secretion in glycoprotein-producing pituitary tumors

To study patterns of hormone production and secretion in glycoprotein-producing pituitary tumors, 12 patients with such tumors underwent the following studies. Preoperatively, all patients had serum TSH, LH, FSH, and alpha-subunit levels measured every 15 min for 24 h. Hormone pulses were located by cluster analysis, and pulse parameters were compared to those in healthy young men, healthy young women, healthy postmenopausal women, and subjects with primary hypothyroidism. After surgery, immunocytochemistry for the four glycoproteins was performed on all tumors, and Northern blot analysis was performed in six tumors with probes for the four subunits. By immunocytochemistry, 42% of the tumors were positive for TSH beta, 83% for LH beta, 75% for FSH beta, and 92% for alpha-subunit. Preoperative serum hormone levels varied widely between patients and were not well correlated with the intensity of immunocytochemical staining. Northern blot analysis did not appear to be as sensitive as immunocytochemistry for detection of the glycoproteins. All patients had pulsatile glycoprotein secretion, with pulses of normal frequency but varied amplitude. These results suggest that in patients with glycoprotein tumors, hormone pulses may be an integral part of autonomous secretion, or that hypothalamic control is involved in glycoprotein secretion and, perhaps, in the pathogenesis of these tumors.

Patterns of pulsatile pituitary glycoprotein secretion in central hypothyroidism and hypogonadism

Five patients with central hypothyroidism and hypogonadism due to mass or infiltrative lesions of the pituitary and hypothalamus were studied to determine pulsatile pituitary glycoprotein secretion patterns. Blood samples were obtained every 15 min over 24 h, and TSH, LH and FSH were measured by immunoradiometric assays. Hormone pulses were located by cluster analysis, and pulse patterns were compared to those in normal subjects. Three patients had unmeasurable LH levels, while two had a normal number of low amplitude pulses. In contrast, all patients had normal FSH pulse frequency, and only one had low pulse amplitude. Three patients had normal 24-h TSH pulse frequency and amplitude, while two had slightly decreased pulse parameters. However, all failed to show normal nocturnal increases in TSH pulse amplitude. Thus, anatomical hypothalamic-pituitary lesions disrupt pulsatile glycoprotein secretion in a discordant fashion. LH is most severely affected, with abnormal pulse patterns similar to those in idiopathic central hypogonadism. FSH and TSH pulses are relatively preserved, but loss of the usual nocturnal increase in TSH pulse amplitude is sufficient to cause clinical hypothyroidism. Whether these defects reflect intrinsic pituitary disease or impaired hypothalamic releasing factor function remains to be determined.

Clinical and molecular studies of a thyrotropin-secreting pituitary adenoma

A 40-year-old woman, who had previously received radioactive iodine for hyperthyroidism, presumably due to Graves' disease, subsequently was found to have inappropriately elevated serum TSH and alpha-subunit levels and a pituitary adenoma. Detailed clinical studies revealed marked serum TSH elevations (approximately 100 mU/L) with no circadian variation, but with 7 pulses/24 h. Serum alpha-subunit levels averaged 2.5 micrograms/L, with 13 pulses/24 h. Neither serum TSH nor alpha-subunit responded to TRH stimulation, nor did serum TSH change during dopamine infusion, but alpha-subunit levels did decline slightly. In contrast, during somatostatin infusion, serum TSH declined to 30% of baseline levels, while alpha-subunit levels did not change. Pituitary adenoma tissue obtained at the time of transsphenoidal surgery immunostained weakly with anti-TSH beta serum and strongly with anti-alpha-subunit serum. Northern blot analysis of RNA isolated from the tumor revealed TSH beta and alpha-subunit mRNA levels of normal length, while primer extension analysis showed a major initiation site for the TSH beta gene that appeared to be identical in the tumor and normal pituitary tissue. A second minor upstream start site was detected in the tumor, but it represented less than 1% of transcription compared to the major downstream start site. We conclude that the tumor secreted TSH and alpha-subunit in an abnormal and discordant fashion, but that the TSH gene initiation site appeared to be normal and, therefore, did not explain the observed secretory abnormalities.