Transcript initiation, polyadenylation, and functional promoter mapping for the dihydrofolate reductase-thymidylate synthase gene of Toxoplasma gondii

The fused dihydrofolate reductase/thymidylate synthase gene of Toxoplasma gondii contains ten exons spanning approximately 8 kb of genomic DNA. We have examined the ends of DHFR-TS transcripts within this gene, and find a complex pattern including two discrete 5' termini and multiple polyadenylation sites. No TATAA box or other classical promoter motif is evident in 1.4 kb of genomic DNA upstream of the coding region, but transcript mapping by RNase protection and primer extension reveals two prominent 5' ends at positions -369 and -341 nt relative to the ATG initiation codon. Upstream genomic sequences include GC-rich regions and the (opposite strand) WGAGACG motif previously identified in other T. gondii promoters. Mutagenesis of recombinant reporter plasmids demonstrates that this region is essential for efficient transgene expression. Sequencing the 3' ends from multiple independent mRNA clones demonstrates numerous polyadenylation sites, distributed over >650 nt of genomic sequence beginning approximately 250 nt downstream of the stop codon. Within this region, certain sites seem to be preferred: 14 different positions were found among the 32 polyadenylated transcripts examined, but approximately 40% of the transcripts map to two loci. The 3' noncoding region is rich in A and T nucleotides, and contains an imperfect 50 nt direct repeat, but no obvious poly(A) addition signal was identified.

Unification of the band anticrossing and cluster-state models of dilute nitride semiconductor alloys

We show that a quantitative description of the conduction band in Ga(In)NAs is obtained by combining the experimentally motivated band anticrossing model with detailed calculations of nitrogen cluster states. The unexpectedly large electron effective mass values observed in many GaNAs samples are due to hybridization between the conduction band edge E- and nitrogen cluster states close to the band edge. Similar effects explain the difficulty in observing the higher-lying E+ level at low N composition. We predict a decrease of effective mass with hydrostatic pressure in many GaNAs samples.

Effectiveness of a formal post-baccalaureate pre-medicine program for underrepresented minority students

PURPOSE

To address the effectiveness of a formal postbaccalaureate (PB) experience for underrepresented minority (URM) students before medical school. The program provided an intense year-long experience of course work, research, and personal development.

METHOD

There were 516 participants from one medical school: 15 URM medical students had completed the formal PB program, 58 students had done independent PB work before matriculation, and 443 students were traditional matriculants. Cognitive and academic indicators [college science and non-science grade-point averages (GPAs); biology, physics, and verbal MCAT scores; and percentage scores from first-year medical school courses] were compared for the three groups.

RESULTS

Both groups of students with PB experience demonstrated competency in the first year of medical school consistent with traditional students even though the students who had completed the formal PB program had lower MCAT scores and lower college GPAs than did the traditional students. Traditional predictors of academic performance during the first year of medical school did not significantly contribute to actual academic performances of students from the formal PB program.

CONCLUSION

The results support the use of a formal PB program to provide academic readiness and support for URM students prior to medical school. Such a program may also improve retention. Noncognitive variables, however, may be important to understanding the success of such students in medical school.

Induction of steroid 21-hydroxylase/beta-galactosidase transgene expression by unilateral adrenalectomy

Unilateral adrenalectomy was used to induce compensatory growth in the contralateral adrenal gland of transgenic mice bearing a steroid 21-hydroxylase promoter/beta-galactosidase reporter (21-OHase/beta-gal) transgene, in which 6.4 kb of 5'-flanking sequence of the mouse steroid 21-OHase A gene are linked to a LacZ reporter gene. 48 hours following removal of the right adrenal gland, the left gland of transgene-positive mice showed a 4.5 fold increase in specific activity of the beta-gal reporter, compared to the right gland, while left glands from sham-operated transgene-positive and unilateral adrenalectomized transgene-negative mice showed no such increase. The increased specific transgene reporter activity, relative to total adrenal gland protein, must result from up-regulation of transgene expression, rather than from the compensatory increase in adrenocortical mass. This suggests that elements regulating trophic hormone-mediated 21-OHase gene expression in vivo are located within 6.4 kb of the 21-OHase gene transcription start site.

Relations between family environment and adjustment outcomes in young adults with spina bifida

Thirty-two young adults with spina bifida completed a questionnaire (Family Environment Scale) assessing their perceptions of family social environment while growing up. Additionally, subjects responded to a structured interview addressing their current employment status, residential situation, level of community mobility, and extent of social activity. Multiple logistic regression analyses were used to assess the relation between family environment and adjustment as a young adult. With this limited sample, results indicated that perceived family environment explained variance in employment, community mobility, and social activity as an adult, even beyond that explained by lesion level and intelligence. Regression coefficients showed positive relations between perceived family encouragement of independence and achievement and young adult outcomes. In contrast, perceived moral/religious emphasis of the family and degree of family involvement with intellectual/cultural activities evidenced negative relations with the measures of young adult adjustment.

Serotonergic inhibition of phrenic motoneuron activity: an in vitro study in neonatal rat

In vitro experiments were conducted on neonatal rat brainstem-spinal cord preparations to test the hypothesis of an inhibitory modulation of phrenic activity by serotonin (5-HT) via non-5-HT2A receptors [Lindsay, A.D. and Feldman, J.L., Modulation of respiratory activity of neonatal rat phrenic motoneurones by serotonin, J. Physiol., 461 (1993) 213-233]. The changes induced by 5-HT and related agents on phrenic root discharges and membrane currents in identified phrenic motoneurons were analysed after blockade of spinal 5-HT2A receptors. Spinal application of 5-HT1B (but not 5-HT1A) receptor agonists depressed the phrenic activity and the effect was prevented by pretreatment with 5-HT1B (but not 5-HT1A, 5-HT2A and 5-HT3) receptor antagonists. Results from phrenic motoneuron whole cell recordings do not reject a presynaptic location of the 5-HT receptors responsible for this depression.

Comparison of clinical manifestations of HIV infection between male and female injecting drug users

OBJECTIVE

To compare occurrence of clinical symptoms, physical examination findings and hematologic variables in male and female HIV-seropositive injecting drug users (IDU) with similar CD4+ lymphocyte counts.

METHOD

We interviewed and examined 118 female and 444 male AIDS-free HIV-seropositive IDU for clinical signs and symptoms. HIV serology and T-lymphocyte subset evaluations were performed. Comparisons were analyzed by Mantel-Haenszel procedures.

RESULTS

In this population, median age for men was 35 years versus 33 years for women; median CD4 cell count was 490 x 10(6)/l for men versus 480 x 10(6)/l for women. The overall frequency of oral candidiasis increased as CD4 cell count decreased, but did not vary by sex. Recent history of genital herpes was more frequent (P < 0.05) in women than men, but this difference was not significant on physical examination. Symptoms of diarrhea, fatigue, weight loss, shortness of breath, presence of enlarged posterior cervical lymph nodes did not vary by CD4 cell count or sex, and no strong interactions were evident. Although absolute values of hematocrit were higher (P < 0.001) and platelet count lower (P < 0.001) in HIV-seropositive men than women, distributions of hematocrit and platelet count by sex were similar for HIV-seropositive participants and HIV-seronegative controls.

CONCLUSION

Our data on IDU prior to a diagnosis of AIDS suggest that constitutional signs and symptoms are generally similar among men and women early in HIV infection. Additional follow-up is needed to determine whether differential rates of signs and symptoms by sex appear with progression of HIV infection.

Human immunodeficiency virus infection in diabetic intravenous drug users

OBJECTIVE

--To evaluate the association between diabetes and human immunodeficiency virus (HIV) seroprevalence in a population of intravenous (IV) drug users.

DESIGN

--Cross-sectional survey in a cohort of IV drug users.

SETTING

--Community-based study clinic.

SUBJECTS

--The study included 2921 individuals with a history of IV drug use in the past 10 years; over 90% had injected drugs in the past year and 77% in the past month; only 15% were receiving drug treatment.

OUTCOME MEASURES

--The HIV seroprevalence among IV drug users with and without a history of diabetes.

RESULTS

--Those IV drug users with a history of diabetes had significantly lower HIV seroprevalence (9.8%) than nondiabetic IV drug users (24.3%; P = .03). Despite similar duration and intensity of drug use and sexual practices, diabetic IV drug users tended not to share injection paraphernalia and were less likely to attend shooting galleries than nondiabetic IV drug users.

CONCLUSION

--Our data suggest that the apparent protective effect of diabetes against HIV infection in IV drug users is most likely due to their safer injection practices afforded by their ready access to sterile injection equipment.

Sexually transmitted diseases in a population of intravenous drug users: association with seropositivity to the human immunodeficiency virus (HIV)

The association between human immunodeficiency virus (HIV) seropositivity and a history of sexually transmitted diseases (STDs), evidence of STDs on physical examination, and sexual and drug use practices was studied in a population of 2921 intravenous drug users (IVDUs) in Baltimore during 1988 and 1989. Overall, 24.1% were HIV-seropositive at baseline, and 60% reported a history of an STD. A significant association was found between HIV seropositivity and a history of syphilis (P = .04); both were more frequent among homosexual/bisexual men than among heterosexual IVDUs. In multivariate analysis, a history of syphilis was independently associated with HIV seroprevalence in homosexual/bisexual male IVDUs, of whom 90% reported a history of sexual intercourse with women. Cocaine injection was independently associated with HIV seropositivity but not a history of syphilis on multivariate analysis. STDs, indicative of unsafe sex practices, are common in this population; efforts are needed to prevent sexual transmission of HIV infection among IVDUs and their sex partners.

Redox chemistry of the 9-anilinoacridine class of antitumor agents

9-Anilinoacridines bearing a 1'-NHR substituent on the anilino ring undergo facile, chemically reversible, two-electron oxidation to quinone diimines. The chemical and electrochemical oxidation of three groups of 9-anilinoacridines (1'-substituted derivatives, together with 3'-substituted analogues and acridine-substituted analogues of the clinical antileukemic drug amsacrine) have been studied and their redox potentials determined. For aniline-substituted derivatives, redox potentials (E1/2) correlate well with substituent electronic properties, with electron-donating substituents facilitating oxidation. Substituents in the acridine ring have little effect on redox potentials, indicating minimal transmission of electronic effects from the acridine to the aniline rings. Although the broad class of 9-anilinoacridines show biological activity over a very wide range of structural variations, a 1'-NHR substituent is a common feature of the most active derivatives. Nevertheless, no clear quantitative relationships between redox potential and biological activity could be discerned, and the relevance of this redox chemistry to the mode of action of amsacrine and other 9-anilinoacridines remains unclear.

Home monitoring of blood pressure: usefulness as a predictor of persistent hypertension

We set out to test the hypothesis that home blood pressure reflects "baseline" pressures measured at a general practitioner's surgery or in a hospital outpatient clinic. Twenty patients detected hypertensive during screening in general practice and 30 patients referred to a hospital hypertension clinic for revision of therapy were studied. All were instructed in the use of an electronic semiautomatic sphygmomanometer and measured blood pressure at home for a three day period. Home monitored blood pressure correctly predicted those patients whose diastolic blood pressure fell to below 95 mmHg by the third clinic visit in approximately 90% of all patients. In addition, in those whose blood pressure was high at home it remained so at the clinic or surgery after three visits. These data suggest that home monitoring of blood pressure may be a helpful alternative to repeated clinic visits before embarking on medical therapy.

Three-dimensional reconstruction from serial sections III. AUTOSCAN, a software package in FORTRAN for semiautomated photomicrography

A FORTRAN program, called AUTOSCAN, is described. This program permits the collection of photomicrographic data from serial sections to be semiautomated. In essence the user defines a box around a microscopic field of interest. Then the program drives the stage incrementally in the x and y directions, taking photographs of contiguous subfields. The box is defined by the use of a joystick and the "return" key. That is, movements of a joystick cause the stage to translate in the x and y directions. When a corner of the object is reached, as defined by cross-hairs in the microscope eyepiece, the user hits the return key. Repetition of this process at each corner defines a "box" within which photographs are to be taken. AUTOSCAN then calculates the step size and the number of frames to be taken from the user-defined values for the magnification. The actual movements of the stage in the x and y directions and the photography are fully automated. Each frame of film has the x and y coordinates of the center of the subfield being photographed imprinted in one corner, along with other relevant data. The x and y coordinates permit the resultant information to be assembled correctly into a two-dimensional montage.

Application of a computerized medical decision-making process to the problem of digoxin intoxication

A computerized medical decision-making system was used to monitor signs and predisposing factors of digoxin intoxication in patients receiving digoxin. This process automatically reviewed the patient's data base nightly for drug interactions, laboratory data and electrocardiographic findings with known association with digoxin intoxication. These decisions were formated into a "digoxin alert report" and sent to line printers in the nursing division to be placed on the individual patients' charts. To assess the effect of these reports on patient management, a randomized double-blind study was undertaken. Patients were assigned to an alert or nonalert group. Alert reports were withheld from charts of patients in the nonalert group. A medical record review was subsequently carried out, wherein the physician's orders were searched to identify actions taken with possible relation to the digoxin alerts. The computer monitored 396 patients over a 3 month period. Of these, 211 (53%) were randomized to the alert group and 185 (47%) to the nonalert group. Seventy-two percent of patients received at least one alert. The most frequently occurring alerts included: hypoxemia, hypokalemia, concurrent use of a beta-adrenergic blocking agent, renal insufficiency and ventricular arrhythmia. Results from the record review demonstrated a 22% increase in physician actions for the alert group. Specifically, patients in the alert group were 2.7 times more likely to have a serum digoxin determination ordered and 2.8 times more likely to have digoxin withheld on the day of a digoxin alert than were patients in the nonalert group.