Tetrahydrobiopterin and biogenic amine metabolism in the hph-1 mouse

hph-1 mice, which have defective tetrahydrobiopterin biosynthesis due to decreased GTP cyclohydrolase I activity, have been used to investigate the effects of tetrahydrobiopterin deficiency on aromatic L-amino acid monooxygenases and brain monoamine metabolism. Liver tetrahydrobiopterin levels were decreased, and tetrahydrobiopterin deficiency and reduced levels of dopamine, norepinephrine, serotonin, and their metabolites in the brain occurred both pre- and postnatally. Chronic subcutaneous tetrahydrobiopterin elevated brain levels to values higher than those seen in controls but had no effect on monoamine metabolism. In vivo activities of tyrosine hydroxylase and tryptophan hydroxylase were significantly decreased. There was a 30% decrease in the in vitro activity of striatal tyrosine hydroxylase and 50% decrease in liver phenylalanine hydroxylase. Western blotting demonstrated that the lower monooxygenase activities resulted from a reduced absolute amount of tyrosine hydroxylase and phenylalanine hydroxylase protein. The findings suggest involvement of tetrahydrobiopterin in the control of the steady-state concentration of the aromatic L-amino acid monooxygenases. In addition, demonstration of central monoamine changes in the hph-1 mouse make it a possible model system for the investigation of the neuropathological mechanisms in Dopa-responsive dystonia, which has recently been linked with mutations in the gene for GTP cyclohydrolase I.     

Intrauterine or oral administration of levonorgestrel in combination with estradiol to perimenopausal women--effects on lipid metabolism during 12 months of treatment

Electrical stimulation of the basal temporal region of the dominant hemisphere before partial temporal lobectomy for epilepsy sometimes produces temporary interruption of language function, but the significance of removal of this area is unknown. We evaluated the correlation between resection of the basal temporal language areas (BTLA) and certain types of postoperative language deficits. In a population of 25 patients, we mapped the inferolateral temporal lobe with cortical electrical stimulation, verifying the positions of the stimulating electrodes with three-dimensional computed tomography (CT). Eighty percent of the patients developed transient language deficits with stimulation, particularly with tests of confrontation naming and comprehension. BTLA was primarily located in the fusiform gyrus, from 1 to 9 cm from the temporal tip. At testing 6-12 months after operation, patients with BTLA resection performed worse (mean 9% decrease) than those with no BTLA resection (mean 4% improvement) on tests of confrontation naming (p = 0.03). Resection size accounted for less of the variance in decrease in confrontation naming than did resection of the BTLA. Tests of performance I.Q. (PIQ), verbal I.Q. (VIQ), or recognition memory for word and verbal learning showed no significant difference between these groups. Most patients do not have language decrease with removal of basal temporal lobe 5-6 cm from the tip, even with removal of BTLA. Some patients, however, have persistent decrease in naming.     

The effects of an outpatient practice guideline at a teaching hospital: a prospective pilot study

BACKGROUND: Platelet-activating factor (PAF) is a bioactive phospholipid which is a potent hypotensive agent. To investigate the role of PAF in renovascular hypertension, we determined the PAF concentration and its production level assessed by the activity of cholinephosphotransferase (CPT) in renal tissue and examined the effect of a PAF antagonist on the mean arterial pressure (MAP) in control and two-kidney with one clipped (2K1C) hypertensive rats. MATERIALS AND METHODS: The concentration of PAF and CPT in the renal medulla and cortex were determined by radioassay. Also, the effect of a PAF antagonist, CV-6209, on MAP was also examined in both 2K1C hypertensive and normal control rats. RESULTS: The PAF concentration and CPT activity were significantly higher in the medulla than in the cortex in both 2K1C hypertensive and normal control rats, and both values in the medulla were also significantly higher in the clipped kidney than in the contralateral unclipped kidney or in control rat kidneys. We also observed a significant negative correlation between the PAF concentration in the medulla, and the medulla weight in the clipped kidney of 2K1C hypertensive rats. Infusion of the PAF antagonist, CV-6209, did not affect MAP in 2K1C hypertensive rats, but was significantly increased (P < 0.05) in control rats. CONCLUSIONS: These findings suggest that PAF, whose production is induced by renal ischemia due to renal artery stenosis, plays an important role in the renomedullary vasodepressor system, but the effect of PAF as a vasodilator in the peripheral vessels is limited in 2K1C hypertension.     

Variants of chromosome 9 in phenotypically normal individuals

The human chromosome 9 displays the highest degree of structural variability. Four different types of variants are described including pericentric inversion, extra G-positive band in the q arm, additional G-positive band in the p arm and duplication of band 9q21-q22. It is important to demonstrate inheritance from a phenotypically normal individual in order to differentiate between a variant chromosome and an abnormal chromosome.     

Retinoid-regulated gene expression in neural development

The discovery and development of information surrounding the retinoic acid receptors (RAR and RXR) has ushered in a new era in understanding the molecular mechanism of action of vitamin A in embryonic development and cellular differentiation. The mechanisms involved in the regulation of gene expression by the retinoids is at least partially known and involves binding of the RAR and RXR to retinoic acid response elements. Additional factors, including coregulatory proteins, associated regulatory elements, and cell-specific factors, may also be involved in determining the specificity of retinoid-regulation of gene expression during development. During embryogenesis, retinoids are required for the development of the posterior hindbrain and its associated structures, as well as for the survival and differentiation of certain classes of neurons and neural crest cell derivatives. At least some of the effects of retinoid on hindbrain development are related to the regulation of Hox gene expression. Additional retinoid-regulated genes have been implicated in nervous system development, and the manner in which they lead to phenotypic changes during embryogenesis remains to be determined.     

Interdisciplinary approach to functional voice disorders: the psychiatrist''s role

The Trichuris muris-mouse model of intestinal helminth infection provides a convenient system to examine the immune mechanisms operating during acute and chronic infection. Particular subsets of helper T lymphocytes (CD4+Th cells) play an important role in regulating infection via the secretion of distinct groups of cytokines. Reciprocal activation of Th cell subsets is associated with either expulsion of the parasites from the intestine (Th2 cells) or chronic infection (Th1 cells). In vivo neutralization experiments using anti-cytokine monoclonal antibodies show that critical cytokines are involved, with interferon-gamma playing an important role in the establishment of chronic trichuriasis and interleukin-4 in expulsion of the parasite from the gut. This model has provided clear evidence of a crucial role for distinct cytokines in mediating host protection against intestinal helminth infection and that manipulation of the immune response through the Th cell-cytokine axis can benefit either the host or the parasite. As such, the T. muris model is poised to generate important new data relevant not only to intestinal helminthiasis but to the wider field of parasite immunity and infection in general.     

Altered ligand dissociation rates in thyrotropin-releasing hormone receptors mutated in glutamine 105 of transmembrane helix III

Glutamine 105 in the third transmembrane helix of the thyrotropin-releasing hormone receptor (TRH-R) occupies a position equivalent to a conserved negatively charged residue in receptors for biogenic amines where it acts as counterion interacting with the cationic amine moiety of the ligand. Maximum levels of response to TRH in oocytes expressing wild-type TRH-Rs were indistinguishable from those of oocytes expressing receptors mutated to Glu, Asn, or Asp in position 105. However, the EC50 values for activation of oocyte responses increased more than 500 times in oocytes expressing mutant Glu105 receptors, in which the amido group of Gln105 has been removed by site-directed mutagenesis. Charge effects do not seem to be involved in the huge effect of mutating Gln105 to Glu, since mutation of Gln105 to Asp induces only a 15-fold increase in EC50. Furthermore, no change in EC50 is observed after mutation of Asn110 to Asp. The affinity shift (identified by changes in EC50 values for systems of comparable efficacy) in Glu105 mutant receptors was partially recovered in oocytes expressing Asn105 mutant receptors. These results and those obtained after substitution of Lys, Leu, Tyr, and Ser for Gln105 suggest that the presence and the correct position of the Gln hydrogen bond-donor amido group are important for normal functionality of the receptor. In wild type or Asp105 mutant receptors showing the same maximal responses, decreases in affinity with TRH and methyl-histidyl-TRH correlated with increased dissociation rates of hormone from the receptor. Rapid dilution experiments following subsecond stimulation indicate that the TRH-R is converted rapidly from a form showing fast dissociation kinetics to a form from which the hormone dissociates slowly. Mutation of residue 105 impairs the receptor shift between these two forms. This effect was demonstrated in a direct way by comparing [3H]methyl-histidyl-TRH dissociation rates in COS-7 cells transfected with either wild type or Asp105 mutant TRH-Rs. Thus, residues located in transmembrane helix III positions equivalent to those of the counterions for biogenic amines, regulate hormone-receptor interactions in the TRH receptor (and perhaps other receptors). Furthermore, the nature of the amino acid in these positions may also play a role, directly or indirectly, in conformational changes leading to receptor activation, and hence to signal transduction.     

Cytogenetic abnormalities and clonal evolution in an adult hepatoblastoma

Hepatoblastomas usually occur in children < 3 years of age, and only occasional adult cases have been described. To date, 20 cytogenetically abnormal childhood hepatoblastomas have been reported. Karyotypic investigations have shown that most hepatoblastomas are diploid or hyperdiploid, often displaying trisomies for chromosomes 2 and 20. We have cytogenetically investigated an adult hepatoblastoma for which no previous karyotypic data exist. A hypertriploid stemline with multiple numerical and structural chromosomal aberrations, including +2 and +20, was found. In addition, the tumor displayed extensive clonal evolution with 11 subclones. Although the tumor thus displayed some chromosomal abnormalities commonly observed in childhood tumors, providing further support for the importance of these abnormalities in the development of hepatoblastoma, the level of genomic complexity seen in the present case has never been described in childhood hepatoblastomas and may suggest a different etiology or pathogenesis.