A germ-line Tsc1 mutation causes tumor development and embryonic lethality that are similar, but not identical to, those caused by Tsc2 mutation in mice.

Tuberous sclerosis (TS) is characterized by the development of hamartomas in various organs and is caused by a germ-line mutation in either TSC1 or TSC2 tumor suppressor genes. From the symptomatic resemblance among TS patients, involvement of TSC1 and TSC2 products in a common pathway has been suggested. Here, to analyze the function of the Tsc1 product, we established a line of Tsc1 (TSC1 homologue) knockout mouse by gene targeting. Heterozygous Tsc1 mutant (Tsc1(+/-)) mice developed renal and extra-renal tumors such as hepatic hemangiomas. In these tumors, loss of wild-type Tsc1 allele was observed. Homozygous Tsc1 mutants died around embryonic days 10.5-11.5, frequently associated with neural tube unclosure. As a whole, phenotypes of Tsc1 knockout mice resembled those of Tsc2 knockout mice previously reported, suggesting that the presumptive common pathway for Tsc1 and Tsc2 products may also exist in mice. Notably, however, development of renal tumors in Tsc1(+/-) mice was apparently slower than that in Tsc2(+/-) mice. The Tsc1 knockout mouse described here will be a useful model to elucidate the function of Tsc1 and Tsc2 products as well as pathogenesis of TS.

Targeted disruption of the homeobox transcription factor Bapx1 results in lethal skeletal dysplasia with asplenia and gastroduodenal malformation.

BACKGROUND: NK homeobox genes have been shown to play important roles in cell-type specification and organogenesis. Murine Bapx1, a member of NK homeobox gene family, is expressed in all the cartilageous tissues that undergo endochondral bone formation, and in gut mesentery during embryogenesis, suggesting that Bapx1 may be a key transcription factor ragulating the development of these organs. RESULTS: We generated Bapx1-deficient mice by gene targeting. Bapx1-/- mice exhibited lethal skeletal dysplasia, with abnormal development of the vertebral column and some craniofacial bones, accompanied with asplenia and gastroduodenal malformation. We showed that the proliferative activity of the sclerotome cells, forming the vertebral column, was significantly reduced in Bapx1-/- embryos. The sclerotome cells of the mutants appeared to migrate and condense normally, but subsequent differentiation into the mature vertebral bodies and intervertebral discs were affected. The sclerotome cells in the vertebral bodies failed to differentiate into hypertrophic chondrocytes, as revealed by the undetected expression of Col10a1 and Osteopontin, and the sclerotome cells in the intervertebral discs failed to express the typical extracellular matrix proteins Col2a1, Col9a2 and aggrecan. Furthermore, we investigated the effect of loss of Bapx1 on the expression of some transcription factors, identified to be expressed in the developing sclerotome and be required for normal development of the vertebral column. Among them, we found that the expression of MFH-1 (mesenchyme forkhead-1), which was reported to regulate the proliferation and differentiation of sclerotome cells, was significantly reduced in ventromedial sclerotome cells in Bapx1-/- mice. CONCLUSION: Our analysis provided evidence that Bapx1 was indispensable for normal development of ventromedial structure of vertebral column and some of craniofacial bones, splenogenesis and morphogenesis of gastroduodenal tract.

Altered cochlear fibrocytes in a mouse model of DFN3 nonsyndromic deafness.

DFN3, an X chromosome-linked nonsyndromic mixed deafness, is caused by mutations in the BRN-4 gene, which encodes a POU transcription factor. Brn-4-deficient mice were created and found to exhibit profound deafness. No gross morphological changes were observed in the conductive ossicles or cochlea, although there was a dramatic reduction in endocochlear potential. Electron microscopy revealed severe ultrastructural alterations in cochlear spiral ligament fibrocytes. The findings suggest that these fibrocytes, which are mesenchymal in origin and for which a role in potassium ion homeostasis has been postulated, may play a critical role in auditory function.

Generation and characterization of mutant mice lacking ryanodine receptor type 3.

The ryanodine receptor type 3 (RyR-3) functions as a Ca2+-induced Ca2+ release (CICR) channel and is distributed in a wide variety of cell types including skeletal muscle and smooth muscle cells, neurons, and certain non-excitable cells. However, the physiological roles of RyR-3 are totally unclear. To gain an insight into the function of RyR-3 in vivo, we have generated mice lacking RyR-3 by means of the gene targeting technique. The mutant mice thus obtained showed apparently normal growth and reproduction. Although Ca2+-induced Ca2+ release from intracellular Ca2+ stores of the mutant skeletal muscle differed in Ca2+ sensitivity from that of wild-type muscle, excitation-contraction coupling of the mutant muscle seemed to be normal. Moreover, we could not find any significant disturbance in the smooth muscle and lymphocytes from the mutant mice. On the other hand, the mutant mice showed increased locomotor activity, which was about 2-fold greater than that of the control mice. These results indicate that the loss of RyR-3 causes no gross abnormalities and suggest that the lack of RyR-3-mediated Ca2+ signaling results in abnormalities of certain neurons in the central nervous system.

Effects of hemodialysis on cerebral circulation evaluated by transcranial Doppler ultrasonography.

BACKGROUND AND PURPOSE: The effects of hemodialysis on the cerebral circulation of humans and the correlation between changes in blood flow velocity in the basal cerebral arteries and those of several physiological variables influenced by hemodialysis have been inadequately studied. METHODS: Blood flow velocities were obtained from the middle cerebral artery and the basilar artery by transcranial Doppler ultrasonography in 27 patients receiving chronic maintenance hemodialysis immediately before and after the procedure. Changes in body weight, hematocrit, blood pressure, and arterial blood gases were recorded simultaneously. RESULTS: There was a significant reduction in mean flow velocity in the middle cerebral artery (P < .01) and the basilar artery (P < .01) after hemodialysis. We observed a significant negative correlation between the relative change in mean flow velocity and the loss of weight after hemodialysis, the amount of fluid removed, and the increase in hematocrit in the middle cerebral artery and the basilar artery. CONCLUSIONS: Hemodialysis and the associated physiological changes can significantly affect the cerebral circulation. Blood flow velocities in the middle cerebral artery and the basilar artery decrease significantly with hemodialysis. The loss of body weight, the amount of fluid removed, and the change in hematocrit significantly correlate with the change in mean flow velocity. The transcranial Doppler method can effectively monitor rapid changes in the cerebral circulation during potentially harmful procedures.

[Therapeutic effect of lisuride maleate on post-stroke depression].

Twenty post-stroke depressive patients who obtained more than 11 points on Self-Rating Questionnaire for Depression, were treated with 0.075 mg/day lisuride maleate for 12 weeks. The drug effect on depression was evaluated quantitatively by the Hamilton Rating Scale for Depression. The relationships between brain CT or MRI and SRQ-D score were investigated in 24 subjects. More than 80% of post-stroke depressive patients improved after lisuride maleate treatment for 8 or 12 weeks. In particular, depressed mood, hypobulia, sleep disturbance, anxiety, etc. were significantly improved compared to the baseline condition. As for the relationships with CT and/or MRI findings, the group with moderate to severe brain atrophy had a significantly higher grade of depressive state than those without.

Reversal of neurological deficits by levallorphan in patients with acute ischemic stroke.

This study was conducted to examine the effect of the intramuscular injection of levallorphan tartrate (1.0 mg), a mixed agonist-antagonist opiate, on the neurological signs, symptoms, and vital signs in 19 patients with acute ischemic stroke. A temporary improvement of hemiplegia or hemiparesis was observed within several minutes after levallorphan injection in 13 of the patients. There were no significant alterations in blood pressure or pulse rate after injection. The findings indicate that levallorphan may have a temporary improving effect on neurological deficits in acute ischemic stroke. In addition, observation of the response to levallorphan may serve to predict the prognosis of the final neurological outcome in this type of patient.