A novel CDK9-associated C-type cyclin interacts directly with HIV-1 Tat and mediates its high-affinity, loop-specific binding to TAR RNA.

The HIV-1 Tat protein regulates transcription elongation through binding to the viral TAR RNA stem-loop structure. We have isolated a novel 87 kDa cyclin C-related protein (cyclin T) that interacts specifically with the transactivation domain of Tat. Cyclin T is a partner for CDK9, an RNAPII transcription elongation factor. Remarkably, the interaction of Tat with cyclin T strongly enhances the affinity and specificity of the Tat:TAR RNA interaction, and confers a requirement for sequences in the loop of TAR that are not recognized by Tat alone. Moreover, overexpression of human cyclin T rescues Tat activity in nonpermissive rodent cells. We propose that Tat directs cyclin T-CDK9 to RNAPII through cooperative binding to TAR RNA.

RNA polymerase II-associated protein (RAP) 74 binds transcription factor (TF) IIB and blocks TFIIB-RAP30 binding.

A set of deletion mutants of human RNA polymerase II-associated protein (RAP) 30, the small subunit of transcription factor IIF (TFIIF; RAP30/74), was constructed to map functional domains. Mutants were tested for accurate transcriptional activity, RAP74 binding, and TFIIB binding. Transcription assays indicate the importance of both N- and C-terminal sequences for RAP30 function. RAP74 binds to the N-terminal region of RAP30 between amino acids 1 and 98. TFIIB binds to an overlapping region of RAP30, localized to amino acids 1-176 (amino acids 27-152 comprise a minimal binding region). The C-terminal region of RAP74 (amino acids 358-517) binds directly and independently to TFIIB. Interestingly, RAP74 blocks TFIIB-RAP30 binding, both by binding TFIIB and by binding RAP30. When the TFIIF complex is intact, therefore, TFIIB-TFIIF contact is maintained through RAP74. If the TFIIB-RAP30 interaction is physiologically important, the TFIIF complex must dissociate within some transcription complexes.

[Diagnosis and surgical treatment of clivus meningioma].

Seven cases of clivus meningioma were operated on. The tumors sized from 5 to 8 cm in diameter. They were classified into 3 types: petroclival (5 cases), clival (1), sphenopetroclival (1). Common symptoms were cranial nerve deficits of fifth, sixth, seventh, eighth and cerebral disturbance of gait. CT was accurate in determining tumor location and size. Vascular displacement and tumor stain were seen of vertebral angiogram. Blood supply to the tumor was derived primarily from branches of the internal, external carotid arteries and vertebral arteries. Temporo-transtentorial approach, combined temporo-transtentorialsuboccipita approach were used to remove the tumor. Total, Subtotal, and large partial resection of tumors was done in three, two and two cases respectively. Intraoperative technical difficulties were discussed. The mortality of the operation was 14.2%.

[Prevention of arrhythmia in rats by puhuang].

I.P. injection (5g crude drug/kg) of water extract of Puhuang (Typha orientalis) to S.D. rats can prevent ventricular fibrillation and sudden death caused by isoproterenol and also arrhythmia induced by the infusion of BaCl2. Water extract of Puhuang can clearly increase the survival rate and also raise the dosage of BaCl2 infusion necessary to cause the death of animals.

[Pregnancy induced hypertension complicated with cerebrovascular accidents].

Fourteen patients suffering from pregnancy induced hypertension (PIH) complicated with cerebrovascular accidents were admitted for treatment from 1977-1990. These were 8 cases of cerebral hemorrhage, 4 cases of cerebral infarction and 2 cases of cerebral arteriovenous malformation with intracerebral hematomas. These accounted for 0.34% of all hospitalized PIH cases during the same period and three died. The mortality rate was 0.72%. The etiology, pathology, brain CT scan features, clinical manifestations and treatment of these accidents were discussed.

A cDNA encoding RAP74, a general initiation factor for transcription by RNA polymerase II.

RAP30/74 (also known as TFIIF, beta gamma and FC is one of several general factors required for initiation by RNA polymerase II. The small RAP30 subunit of RAP30/74 binds directly to polymerase and appears structurally and functionally homologous to bacterial sigma factors in their RNA polymerase-binding region. RAP30/74 or recombinant RAP30 suppresses nonspecific binding of RNA polymerase II to DNA and is required for RNA polymerase II to assemble stably into a preinitiation complex containing promoter DNA and the general factors TFIID, TFIIA and TFIIB; both RAP30 and RAP74 are physical components of the preinitiation complex. A complementary DNA encoding human RAP30 has been isolated, and here we report the isolation of a cDNA encoding human RAP74. RAP30 and RAP74 produced in Escherichia coli can be used in place of natural human RAP30/74 to direct accurate transcription initiation by RNA polymerase II in vitro.

In vivo release of norethindrone coupled to a biodegradable poly(alpha-amino acid) drug delivery system.

The in vivo release of norethindrone from a biodegradable steroid-polymer conjugate was studied in rats. The drug-polymer conjugate, consisting of [3H]norethindrone coupled via a 17-carbonate bond to poly-N5-(3-hydroxypropyl)-L-glutamine was administered to female rats by subcutaneous injection. The in vivo release of steroid, determined by measuring the daily radioactivity output in urine and feces, was fairly constant though it showed a gradual decrease during the 9-month study period. The data indicate that this biodegradable norethindrone-polymer conjugate is a potential candidate for the controlled delivery of norethindrone to effect long-term contraception.

Physiologic pharmacokinetic model of iopanoic acid metabolism in rats.

The kinetics of iopanoate metabolism have been examined using a physiologic and pharmacokinetic model in rats. The kinetics of iopanoic acid concentration in blood and in eight other major tissue distribution compartments have been determined and fitted to computer-generated concentrations based on a well-established pharmacokinetic model. The results of these studies in nonfasted, conscious rats revealed that after gastric administration of the contrast material tissue concentrations never exceed 30 microgram/g even in the liver. In addition, a clear-cut enterohepatic circulation of the drug was noted in the experimental setting and had to be incorporated into a computer-generated model to account for differences in the predicted model as compared to the experimental data. Such data point out the importance of knowledge of pharmacokinetics of a drug for development of more appropriate dosage regimens of older compounds, theoretical design and testing of new compounds, or to explain clinically observed drug-related phenomenon.

Biophysical characterization of normal T-lymphocytes and Sézary cells.

Blood lymphocytes from 18 patients with cutaneous T-cell lymphoma (Sézary syndrome and mycosis fungoides) were characterized using multiparameter laser flow microfluorimetry (FMF) and automated image analysis (AIA) and the results correlated with routine blood smears, cytogenetic studies and observations made on PHA-stimulated normal T-lymphocytes in vitro. Specimens from all 9 patients with Sézary syndrome and 5 of 9 patients with mycosis fungoides contained one or more discrete subpopulations of neoplastic (Sézary) lymphocytes that were detected by FMF. Studies with AIA demonstrated that neoplastic T-lymphocytes are distinguished from normal quiescent (G0) lymphocytes not only by alterations in DNA content (aneuploidy) but also by chromatin structuring (increased chromatin dispersion), which may be a more sensitive index of neoplastic transformation than ploidy levels. In several patients, small and large Sézary cells were present with DNA-chromatin properties quite similar to normal cycling G1 and G2 lymphocytes respectively, but their presence was not explained by an increase in proliferative activity in the blood. These findings indicate that Sézary syndrome consists of a heterogeneous group of related disorders differing in terms of the Sézary cell population. The response to treatment and prognosis may differ accordingly.

Gastrointestinal radiology. A study of iopanoate metabolism and toxicity in isolated cell cultures.

Radiologists are familiar with certain toxic manifestations of biliary and urinary contrast media (ie, acute tubular necrosis in dehydrated patients with diabetes or multiple myeloma), and with the specific effects of contrast media on other diagnostic tests (ie, I uptake, PBI, etc). These have been studied because of their clinical and diagnostic impact upon patient management. It has become apparent that many subtle, though perhaps predictable, drug interactions occur. Some of these are of obvious clinical and therapeutic significance and have been studied and described in detail. The authors have tried to establish the effects of clinically used drugs on the contrast medium iopanoic acid. The fact that both drugs thus far studied - aspirin and cholestyramine - have profound laboratory effects on iopanoic acid suggests that some systematic approach to the study of the clinical pharmacology of contrast agents is desirable. Others have also observed effects of contrast media on various clinical and laboratory parameters, but most observations are isolated empirical observations, and our basic understanding of the mechanisms involved are crude at best. How might this problem be approached? Although in vivo pharmacokinetic studies in unanesthetized animals allow identification of possible drug-drug interactions in the absence of multiple clinical variables and let us do crossover studies with each animal acting as its own control, such studies are difficult, expensive, and do little to establish the mechanism of the interaction. The authors are currently approaching this problem with a more basic technique. In conjunction with colleagues in gastroenterology and pharmacy, they are studying iopanoate metabolism and aspirin-iopanoate interaction in isolated hepatocyte monolayer cultures. The preliminary data from these experiments will be presented, and the significance of these results and the potential usefulness of this model will be discussed.