Transcriptional regulation of vav, a gene expressed throughout the hematopoietic compartment

The vav gene is expressed in all hematopoietic but few other cell types. To explore its unusual compartment-wide regulation, we cloned the murine gene, sequenced its promoter region, identified DNase I hypersensitive (HS) sites in the chromatin, and tested their promoter activity with a beta-galactosidase (beta-gal) reporter gene in cell lines and transgenic mice. Whereas fibroblasts had no HS sites, a myeloid and an erythroid cell line contained five, located 0.2 kb (HS1), 1.9 kb (HS2), and 3.6 kb (HS3) upstream from the transcription start and 0.6 kb (HS4) and 10 kb (HS5) downstream. A vav DNA fragment including HS1 promoted beta-gal expression in a myeloid but not a fibroblast line. Expression in leukocytes of transgenic mice also required HS2 and HS5. Only hematopoietic organs contained beta-gal, but virtually all beta-gal+ cells were B or T lymphocytes. Expression was always variegated (mosaic), and the proportion of beta-gal+ cells declined with lymphoid maturation and animal age. Thus, these vav regulatory elements promoted hematopoietic-specific expression in vivo, at least in lymphocytes, but the transgene was sporadically silenced. Maintaining pan-hematopoietic expression may require additional vav elements or an alternative reporter.

Bim: a novel member of the Bcl-2 family that promotes apoptosis

Certain members of the Bcl-2 family inhibit apoptosis while others facilitate this physiological process of cell death. An expression screen for proteins that bind to Bcl-2 yielded a small novel protein, denoted Bim, whose only similarity to any known protein is the short (nine amino acid) BH3 motif shared by most Bcl-2 homologues. Bim provokes apoptosis, and the BH3 region is required for Bcl-2 binding and for most of its cytotoxicity. Like Bcl-2, Bim possesses a hydrophobic C-terminus and localizes to intracytoplasmic membranes. Three Bim isoforms, probably generated by alternative splicing, all induce apoptosis, the shortest being the most potent. Wild-type Bcl-2 associates with Bim in vivo and modulates its death function, whereas Bcl-2 mutants that lack survival function do neither. Significantly, Bcl-xL and Bcl-w, the two closest homologues of Bcl-2, also bind to Bim and inhibit its activity, but more distant viral homologues, adenovirus E1B19K and Epstein-Barr virus BHRF-1, can do neither. Hence, Bim appears to act as a 'death ligand' which can only neutralize certain members of the pro-survival Bcl-2 sub-family.

Determinants of abnormal gonadotropin secretion in clinically defined women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder of reproductive age women characterized in its broadest definition by the presence of oligoamenorrhea and hyperandrogenism and the absence of other disorders. Defects of gonadotropin secretion, including an elevated LH level, elevated LH to FSH ratio, and an increased frequency and amplitude of LH pulsations have been described, but the prevalence of these defects in a large, unbiased population of PCOS patients has not been determined. Sixty-one women with PCOS defined by oligomenorrhea and hyperandrogenism and 24 normal women in the early follicular phase had LH samples obtained every 10 min for 8-12 h. Pool LH levels from the frequent sampling studies were within the normal range in the 9 PCOS patients (14.8%) who were studied within 21 days after a documented spontaneous ovulation. Excluding these post-ovulatory patients, 75.0% of the PCOS patients had an elevated pool LH level (above the 95th percentile of the normal controls), and 94% had an elevated LH to FSH ratio. In the anovulatory PCOS patients, pool LH correlated positively with 17-OH progesterone (R = 0.30, P = 0.03), but not with estradiol, estrone, testosterone, androstenedione, or DHEA-S. Pool LH and LH to FSH ratio correlated positively with LH pulse frequency (R = 0.40, P = 0.004 for pool LH, and R = 0.39; P = 0.005 for LH/FSH). There was also a strong negative correlation between pool LH and body mass index (BMI) (R = -0.59, P < 10(-5)). The relationship between BMI and LH secretion in the PCOS patients appeared to be strongest with body fatness, as pool LH was correlated inversely with percent body fat, whether measured by skinfolds (R = -0.61, P < 10(-5)), bioimpedance (R = -0.55, P < 10(-4)), or dual energy x-ray absorptiometry (DEXA) (R = -0.70, P = 0.001; n = 18 for DEXA only). By DEXA, the only body region that was highly correlated with pool LH was the trunk (R = -0.71, P = 0.001). The relationship between body fatness and LH secretion occurred via a decrease in LH pulse amplitude (R = -0.63, P < 10(-5) for BMI; R = -0.58, P < 10(-4) for bioimpedance; and R = -0.64, P = 0.004 for whole body DEXA), with no significant change in pulse frequency with increasing obesity (R = -0.17, P = 0.23 for BMI).

IN CONCLUSION

1) the prevalence of gonadotropin abnormalities is very high in women with PCOS selected on purely clinical grounds, but is modified by recent spontaneous ovulation; 2) the positive relationship between LH pulse frequency and both pool LH and LH to FSH ratio supports the hypothesis that a rapid frequency of GnRH secretion may play a key etiologic role in the gonadotropin defect in PCOS patients; 3) pool LH and LH pulse amplitude are inversely related to body mass index and percent body fat in a continuous fashion; and 4) the occurrence of a continuous spectrum of gonadotropin abnormalities varying with body fat suggests that nonobese and obese patients with PCOS do not represent distinct pathophysiologic subsets of this disorder.

Resource utilization among neonatologists in a university children's hospital

OBJECTIVE

We studied factors affecting length of hospital stay and resulting hospital charges among patients managed by two separate groups of neonatologists in the same academic health science center.

DESIGN

Retrospective analysis of clinical and financial data base information.

METHODS

Neonatal intensive care was provided in the same acute care nursery in a large university children's hospital by: (1) neonatologists in a full-time academic division (group A) and (2) a group associated with a private managed care organization (group B). Clinical and financial parameters of all neonates admitted in fiscal year 1994 were compared for the two provider groups. Stepwise regression analysis was used to evaluate factors influencing hospital charges and length of hospital stay (LOS) and to adjust for differences in clinical variables between the two groups.

RESULTS

Group A physicians provided care for 340 infants, while 137 were treated by those of group B. Group A included older patients, more outborns, more level III patients, more sepsis, more intermittent positive pressure ventilation, and more patent ductus arteriosus. The incidence of transient tachypnea of the newborn was higher among group B patients. Hospital charges were primarily determined by LOS, which was similar for the two groups. When the data were corrected for differences in risk and patient acuity, however, a significant relationship between physician group and LOS was demonstrated, with LOS being an average of 7.8 days shorter for group A. A net reduction of $3 114 969 in hospital charges might have been realized had group A physicians provided care for all study patients.

CONCLUSIONS

Hospital charges were determined by LOS. In this setting, academic neonatologists produced shorter LOS and comparable clinical outcomes, despite caring for a population at greater risk. The reduction in LOS could have resulted in more than $3.1 million in annualized savings had the academic group provided care for all of the study patients.

Effects of spontaneous gastric hypoacidity on the pharmacokinetics of zidovudine and didanosine

STUDY OBJECTIVE

To determine the effect of spontaneous gastric hypoacidity on the pharmacokinetics of zidovudine and didanosine in subjects infected with the human immunodeficiency virus (HIV).

DESIGN

Controlled, open-label, single-dose, pharmacokinetic study.

SUBJECTS

Thirty-two asymptomatic HIV-infected subjects.

INTERVENTIONS

Gastric pH studies were conducted in all 32 subjects, and 20 of these subjects (8 women, 12 men) were enrolled into the pharmacokinetic study. They were stratified into two groups according to fasting gastric pH: those without and with gastric hypoacidity (minimum gastric pH < 3 and > or = 3, respectively). Gastric pH was measured using the Heidelberg pH monitoring system in all subjects before and during pharmacokinetic analysis of zidovudine 100 mg or didanosine 200 mg (given as two 100-mg tablets dissolved in 6 oz water). Plasma samples were collected over 8 hours after dosing.

MEASUREMENTS AND MAIN RESULTS

Six (20%) of 30 subjects had a minimum gastric pH of 3 or above on at least two occasions, and the remaining 2 had variable gastric pH. Although gastric pH was unchanged during the administration of zidovudine, it increased to greater than 9 in 11 of 12 subjects with didanosine, regardless of baseline value. For both drugs, there were no statistically significant differences in peak plasma concentration (Cmax), time to reach peak plasma concentration (Tmax), elimination rate constant (ke), and area under the plasma concentration-time curve from time zero to infinity (AUC0-infinity) between subjects with and without gastric hypoacidity despite sufficient statistical power to detect a 56% difference in clearance for either drug (alpha 0.05, beta 0.1).

CONCLUSION

Gastric hypoacidity occurs in approximately 20% of HIV-infected patients and does not appear to influence zidovudine or didanosine pharmacokinetics.

Bcl-2 has a cell cycle inhibitory function separable from its enhancement of cell survival

Myeloid maturation appears to require exit from the cell cycle and leads to activation of apoptosis in the differentiated cells. The level of Bcl-2, which is known to promote cell survival, is shown here to influence both these critical steps. Bcl-2 function during myelomonocytic differentiation was investigated by introducing a deregulated bcl-2 gene into HL60 promyelocytic leukemia cells, which can be induced to exit the cell cycle and differentiate into granulocytes or monocytes. Deregulated Bcl-2 expression did not itself promote differentiation but extended the lifespan of mature cells elicited by granulocytic or monocytic inducers. Unexpectedly, in response to induction, Bcl-2 overexpression markedly potentiated and hastened cell cycle withdrawal into G(0). Enhanced survival cannot account for the elevated numbers of G(0) cells, because they arose under induction conditions that did not kill control cells. Since the cell cycle status and growth of uninduced cells was not affected by Bcl-2-overexpression, its cell cycle inhibitory activity must require an induction signal. While cell cycle withdrawal may be necessary for maturation, it was not sufficient, implicating a requirement for specific differentiative signals. These results identify, for the first time, a function for the bcl-2 proto-oncogene that is separable from its enhancement of cell survival.

Lessons from bcl-2 transgenic mice for immunology, cancer biology and cell death research

The protein product of the proto-oncogene bcl-2, originally discovered by virtue of its chromosomal translocation in human follicular centre B cell lymphoma, is a physiological inhibitor of programmed cell death, apoptosis. Initial studies in transgenic mice overexpressing Bcl-2 in B or T lymphocytes demonstrated that Bcl-2 can potently antagonise cell death induced by multiple independent signal transduction routes and can contribute to oncogenesis, particularly in combination with other oncogenes, like c-myc, that promote cell proliferation. Further investigations using crosses between bcl-2 transgenic mice and T cell receptor or immunoglobulin transgenic mice or mutant mice deficient in proper antigen receptor gene rearrangement demonstrated that Bcl-2 can only block death of cells that failed to receive a positive stimulus, "death by neglect', but not activation induced apoptosis. Collectively, these results provide evidence that distinct signalling pathways for apoptosis converge upon a common effector machinery where Bcl-2 acts as an antagonist, but that there also exists a mechanism that can either bypass the Bcl-2 checkpoint or override its protective function. These experimental data are reviewed here and discussed in context of current knowledge of lymphocyte differentiation, tumorigenesis and cell death regulation.

A randomized, controlled trial of estradiol replacement therapy in women with hypergonadotropic amenorrhea

Premature ovarian failure is classically defined as menopause occurring before age 40 and is associated with elevated serum FSH levels. If elevated FSH levels indicate lack of ovarian feedback and depletion of primordial follicles, women with prematurely elevated FSH levels should have infertility. However, there are many reports of pregnancies in affected women occurring during estrogen therapy leading to the hypothesis that estrogen may have a salutary effect on folliculogenesis and conception. This randomized, controlled trial was designed to investigate whether estrogen replacement therapy offered a significant therapeutic benefit in hypergonadotropic amenorrhea and to evaluate the potential pathophysiologic mechanisms that would explain the reported pregnancies. Thirty seven women, aged 16 to 40, with menstrual dysfunction and documented FSH levels elevated above the 95% confidence limits of the mid-cycle gonadotropin peak of the normal menstrual cycle (> 40 IU/L 2nd IRP hMG in our RIA) on at least two occasions, entered the study. The average duration of their amenorrhea was 15.9 months (range 2-96 months). Subjects were randomized to begin estradiol replacement (micronized estradiol [Estrace TM], 2 mg orally each day) or no therapy for 6 weeks in a 12-week, cross-over design with weekly monitoring by both pelvic ultrasonography and serum hormone levels. Thirty-one women completed the entire randomized study. As expected, estradiol therapy increased mean serum estradiol levels by 98 pg/mL and was associated with a significant decrease in mean LH and FSH levels (LH: 45.4 IU/L 2nd IRP hMG vs. 37.1 IU/L, FSH: 63.4 IU/L vs. 40.6 IU/L, geometric means). However, there was no effect of estradiol replacement on mean ovarian volume, the number or size of new follicles, or the ovulation rate in all subjects or in the subset with no identified cause for their hypergonadotropic hypogonadism (n = 20). Two pregnancies occurred during the randomized trial, one on and one off estradiol. In both arms of the study, the majority of subjects developed cystic ovarian structures by ultrasound that were temporally associated with increasing serum estradiol levels, indicating functional ovarian follicles. Seventy-eight percent of all subjects grew at least one new follicle over 10 mm in diameter and 46% ovulated at least once, as determined by a serum progesterone level more than 4 ng/mL. Although ovulations were significantly more common in the 10 women subjects who had less than 3 months of amenorrhea (all of whom ovulated) than in the 27 with greater than 3 months of amenorrhea (only 7 of whom ovulated (26%), P < 0.001), there was no significant difference in eventual pregnancies (2 of the 10 women with less than 3 months of amenorrhea vs. 3 of the 27 with greater than 3 months of amenorrhea, P = 0.47). We conclude that in hypergonadotropic women with amenorrhea: 1) folliculogenesis occurs often but is less frequently followed by ovulation and rarely by pregnancy, suggesting that elevated FSH is a marker of oocyte dysfunction occurring distinct from and earlier than granulosa cell or follicular dysfunction; and 2) estrogen therapy does not improve the rate of folliculogenesis or ovulation.

bcl-w, a novel member of the bcl-2 family, promotes cell survival

The prototypic mammalian regulator of cell death is bcl-2, the oncogene implicated in the development of human follicular lymphoma. Several homologues of bcl-2 are now known. Using a PCR-based strategy we cloned a novel member of this gene family, denoted bcl-w. The gene, which is highly conserved between mouse and human, resides near the T-cell antigen receptor alpha gene within the central portion of mouse chromosome 14 and on human chromosome 14 at band q11. Enforced expression of bcl-w rendered lymphoid and myeloid cells refractory to several (but not all) cytotoxic conditions. Thus, like Bcl-2 and Bcl-x, the Bcl-w protein promotes cell survival, in contrast to other close homologues, Bax and Bak, which facilitate cell death. Comparison of the expected amino acid sequence of Bcl-w with that of these relatives helps to delineate residues likely to convey survival or anti-survival function. While expression of bcl-w was uncommon in B or T lymphoid cell lines, the mRNA was observed in almost all murine myeloid cell lines analysed and in a wide range of tissues. These findings suggest that bcl-w participates in the control of apoptosis in multiple cell types. Its functional similarity to bcl-2 also makes it an attractive candidate proto-oncogene.

Comparison of the Omron HEM-713C automated blood pressure monitor with a standard ausculatory method using a mercury manometer

OBJECTIVES

To compare the Omron HEM-713C automated blood pressure machine with the standard ausculatory method using a mercury manometer.

DESIGN

Blood pressures of randomly selected subjects were measured using both the Omron HEM-713C and the mercury manometer.

SETTING

Dombotombo surburb in Marondera, Zimbabwe.

SUBJECTS

One hundred and sixteen subjects 25 years and above (47 males and 69 females) randomly selected in Marondera.

MAIN OUTCOME MEASURE

Systolic blood pressure and diastolic blood pressure.

RESULTS

The Omron HEM-713C passed with a grade B for both systolic and diastolic blood pressures when using the British Hypertension Society protocol. It also passed both systolic and diastolic criteria for Association of the Advancement of Medical Instrumentation.

CONCLUSION

The Omron HEM-713C compares well with the standard mercury manometer, we therefore recommend its use in both research and clinical applications which require blood pressure measurements.

Hlx homeo box gene is essential for an inductive tissue interaction that drives expansion of embryonic liver and gut

The divergent murine homeo box gene Hlx is expressed in restricted hematopoietic cell types and, during embryogenesis, prominently in visceral mesenchyme of the developing liver, gall bladder, and gut. Targeted disruption of the gene has now established that it plays a key role in visceral organogenesis. Embryos homozygous for the mutation died around embryonic day 15 with anemia and severe hypoplasia of the liver and gut. Liver ontogeny commenced normally with formation of the liver diverticulum and differentiation of hepatocytes, but the organ failed to expand and reached only 3% of normal size. The apparent liver hypoplasia was not associated with a notable increase in apoptotic cells. Gut development also began normally, but the intestines failed to undergo extensive elongation and looping and reached only a quarter of normal length. The anemia resulted from a deficiency in the fetal form of hematopoiesis, which occurs in the liver, but no intrinsic defect in Hlx-/- hematopoietic cells was observed in vitro, and liver-derived Hlx-/- hematopoietic stem cells that were transplanted to irradiated normal mice could fully reconstitute hematopoiesis. The impaired fetal hematopoiesis therefore reflects insufficient support function provided by the minute liver. Hlx is normally expressed in visceral mesenchyme lying adjacent to the developing liver and gut epithelia affected by the mutation, but not in the epithelia themselves. Hence, Hlx regulates a mesenchymal-epithelial interaction that drives a vital growth phase in visceral organogenesis. Moreover, because mutation of Hlx blocked liver growth but not its specification, early morphogenesis, or differentiation, development of this organ appears to occur by step-wise inductive interactions under separate genetic control.

Comparison of the morbidity associated with maxillary fractures treated by maxillomandibular and rigid internal fixation

OBJECTIVE

To compare the type and incidence of morbidity encountered by two groups of patients with maxillary fractures, one treated by closed reduction and maxillomandibular fixation and the other by open reduction and rigid internal fixation.

STUDY DESIGN

This was a retrospective review of records for all patients with maxillary fractures treated over a 10-year period. Age, sex, mechanism of injury, anatomic location of fracture, treatment modality, and complications were identified. Two populations of patients, those treated with closed reduction and maxillomandibular fixation and those treated with open reduction and rigid internal fixation, that were similar in size (n = 50), age, sex, and anatomic distribution of fractures were compared.

RESULTS AND CONCLUSIONS

This study indicates that patients with maxillary fractures treated with either closed reduction and maxillomandibular fixation or open reduction and rigid internal fixation will encounter postoperative problems with a near equal frequency (60% to 64%). Regardless of the technique used, no relationship could be established between age, sex, or cause of injury. The more superior the level of the fracture, the higher the rate of adverse sequelae.

Peru-15, an improved live attenuated oral vaccine candidate for Vibrio cholerae O1

Cholera vaccine candidate Peru-15 was derived from a Vibrio cholerae O1 El Tor Inaba strain by deleting the cholera toxin genetic element, introducing the gene encoding cholera toxin B subunit into recA, and screening for nonmotility. In a controlled study, Peru-15 (2 x 10(8) cfu) was administered to 11 volunteers. No vaccinee developed diarrhea, and 10 of 11 had > 4-fold rises in vibriocidal antibody titers. One month later, 5 vaccinees and 5 control volunteers were challenged with wild type V. cholerae O1. Four of 5 controls developed diarrhea (mean, 1.9 L). Two Peru-15 vaccinees developed diarrhea, 1 with < 0.3 L and 1 with approximately 1.0 L; this latter volunteer had not developed a significant vibriocidal immune response to vaccination. Peru-15 shows promise as a single-dose, oral cholera vaccine that is safe, immunogenic, and protective.

Absence of p53 allows direct immortalization of hematopoietic cells by the myc and raf oncogenes

The p53 tumor suppressor is implicated here as a crucial barrier to unlimited cell proliferation. Its role in transformation of hematopoietic cells was studied by infecting fetal liver cells from wild-type or p53-/- mice with oncogenic retroviruses. Transformed colonies arose with a raf and a myc-raf virus. Absence of p53 did not affect their frequency but proved critical for their continued propagation. Colonies of p53-/- cells bearing both myc and raf readily yielded continuous cell lines without apparent requirement for genetic alteration. The lines, mainly of erythroid or myelomonocytic origin, were diploid but highly tumorigenic from their inception. These findings imply that p53 loss contributes directly to immortalization and tumorigenesis, probably by abrogating an intrinsic senescence program.

Overexpressed max is not oncogenic and attenuates myc-induced lymphoproliferation and lymphomagenesis in transgenic mice

The cellular growth promoting function of the Myc oncoprotein requires its heterodimerization with the Max protein, but Max can also form complexes that inhibit Myc action. To determine whether max overexpression in vivo is oncogenic and whether it can modulate the action of Myc, we generated transgenic mice in which the max gene was directed to express in lymphoid cells by a linked immunoglobulin heavy chain enhancer (E mu). Expression of the transgene at substantially higher levels than the endogenous max gene did not perturb lymphoid homeostasis in adult animals nor predispose to lymphomagenesis. The numbers of B-lymphoid cells in very young animals were reduced. Moreover, analysis of bi-transgenic E mu-myc/E mu-max mice revealed that max overexpression attenuated the premalignant B-lymphoproliferative state induced by an E mu-myc transgene and reduced the rate of lymphoma onset. These results suggest that elevation of Max expression in vivo inhibits the function of Myc.

Perturbed development of T and B cells in mice expressing an Hlx homeobox transgene

Within the lymphoid compartment of mice, the Hlx homeobox gene is expressed only at early stages of B-lymphoid differentiation. To determine whether Hlx influences lymphopoiesis, transgenic mice were developed to enforce Hlx expression throughout the B and T cell lineages. The strain with the highest transgene expression in both cell types (Hlx-94) exhibited marked perturbations in both B and T cell development. In these mice, the thymus lacked almost all mature CD4+8- and CD8+4- cells and the medulla was greatly shrunken, whereas nearly one-half the T cells in the periphery were CD4+8+, a cell type normally confined to the thymus. The peripheral CD4+8+ cells had some features of mature T cells, including responsiveness to mitogens. Presumably these cells had emigrated prematurely from the thymus and generated mature T cells in the periphery. Bone marrow transplantation experiments indicated that the defects was intrinsic to the Hlx-94 hematopoietic cells rather than support cells. Although thymocyte development in Hlx-94 mice was blocked at the stage when selection normally occurs, analysis of lymphocyte populations in the progeny of crosses with mice transgenic for an anti-HY T cell receptor indicated that neither positive nor negative selection of T cells was markedly affected. In addition to T cell defects, Hlx-94 mice had subnormal numbers of B lymphoid cells in the bone marrow and spleen, and their surface phenotype suggested that B cell development after the pro-B stage was impeded. Furthermore, the B cell response to stimulation with LPS was impaired. These striking developmental defects suggest that the Hlx gene may help to govern lymphoid maturation.

Perturbed development of T and B cells in mice expressing an Hlx homeobox transgene

Within the lymphoid compartment of mice, the Hlx homeobox gene is expressed only at early stages of B-lymphoid differentiation. To determine whether Hlx influences lymphopoiesis, transgenic mice were developed to enforce Hlx expression throughout the B and T cell lineages. The strain with the highest transgene expression in both cell types (Hlx-94) exhibited marked perturbations in both B and T cell development. In these mice, the thymus lacked almost all mature CD4+8- and CD8+4- cells and the medulla was greatly shrunken, whereas nearly one-half the T cells in the periphery were CD4+8+, a cell type normally confined to the thymus. The peripheral CD4+8+ cells had some features of mature T cells, including responsiveness to mitogens. Presumably these cells had emigrated prematurely from the thymus and generated mature T cells in the periphery. Bone marrow transplantation experiments indicated that the defects was intrinsic to the Hlx-94 hematopoietic cells rather than support cells. Although thymocyte development in Hlx-94 mice was blocked at the stage when selection normally occurs, analysis of lymphocyte populations in the progeny of crosses with mice transgenic for an anti-HY T cell receptor indicated that neither positive nor negative selection of T cells was markedly affected. In addition to T cell defects, Hlx-94 mice had subnormal numbers of B lymphoid cells in the bone marrow and spleen, and their surface phenotype suggested that B cell development after the pro-B stage was impeded. Furthermore, the B cell response to stimulation with LPS was impaired. These striking developmental defects suggest that the Hlx gene may help to govern lymphoid maturation.

The C-terminal zinc finger of GATA-1 or GATA-2 is sufficient to induce megakaryocytic differentiation of an early myeloid cell line

The GATA-1 and GATA-2 transcription factors, which each contain two homologous zinc fingers, are important hematopoietic regulators expressed within the erythroid, mast cell, and megakaryocytic lineages. Enforced expression of either factor in the primitive myeloid line 416B induces megakaryocytic differentiation. The features of their structure required for this activity have been explored. The ability of 12 GATA-1 mutants to promote 416B maturation was compared with their DNA-binding activity and transactivation potential. Differentiation did not require any of the seven serine residues that are phosphorylated in vivo, an N-terminal region bearing the major transactivation domain, or a C-terminal segment beyond the fingers. Removal of a consensus nuclear localization signal following the second finger did not block differentiation or nuclear translocation. The N-terminal finger was also dispensable, although its removal attenuated differentiation. In contrast, the C-terminal finger was essential, underscoring its distinct function. Remarkably, only 69 residues spanning the C-terminal finger were required to induce limited megakaryocytic differentiation. Analysis of three GATA-2 mutants led to the same conclusion. Endogenous GATA-1 mRNA was induced by most mutants and may contribute to differentiation. Because the GATA-1 C-terminal finger could bind its target site but not transactivate a minimal reporter, it may direct megakaryocytic maturation by derepressing specific genes and/or by interacting with another protein which provides the transactivation function.

Cisternal Na+ transport inhibition and the ventilatory response to CO2

When PCO2 rises transiently, glia or neurons may move ions across their cell membranes to restore intracellular pH, in the process changing extracellular pH. Inhibiting ion transport would result in a different extracellular fluid pH (a putative stimulus for the medullary chemoreceptors) and, therefore, in an altered ventilation in response to PCO2. We infused two ion transport inhibitors, amiloride and bumetanide, into the cisterna magna of anesthetized rabbits and compared their ventilatory response to a rebreathing maneuver with sham rabbits receiving no inhibitor. Amiloride (10(-5)-10(-3) M) had no effect; 3 h of 10(-2) M amiloride increased the frequency of breathing and decreased tidal volume but had no net effect on minute ventilation. Bumetanide (10(-3) M) had no effect after 1 h of infusion, but by 3 h it had decreased tidal volume and minute ventilation at 6 and 7% end-tidal CO2 fraction, respectively, during the rebreathe. Three hours of infusion of amiloride and bumetanide did not affect ventilation in a manner consistent with our predictions from previous studies of ionic changes in cerebrospinal fluid. During the 1st h, when neuronal and glial ion transport in the ventrolateral medulla should be inhibited, we found no effect of ion transport inhibition. We conclude that, during the transient hypercapnia of a rebreathing maneuver, Na+/H+ exchange and Na(+)-K(+)-2Cl- cotransport do not play a significant role in immediate rapid pH homeostasis by cellular ion transport in the microenvironment of the medullary chemoreceptors.

Stability and activity of intravenous immunoglobulin with neonatal dextrose and total parenteral nutrient solutions

OBJECTIVE

To determine in vitro the compatibility of reconstituted intravenous immunoglobulin (IVIG) (Gammagard, Baxter-Hyland) with five different neonatal and pediatric intravenous solutions in Viaflex polyvinyl chloride bags.

DESIGN

In vitro compatibility study.

INTERVENTIONS

Samples were taken at time = 0, 10, 30, 60, 90, and 120 minutes and at 4, 8, 12, and 24 hours and assayed for total immunoglobulin G content and antibodies to hepatitis B surface antigen. Type III group B Streptococcus (GBS) and opsonic activity for type III GBS were analyzed at time = 0, 60, and 120 minutes and 12 and 24 hours. All results were compared with those from pure IVIG.

RESULTS

Our results demonstrate that mixing IVIG with intravenous solutions commonly used in the care of premature infants (dextrose 5% in water [D5W], D15W, D5W/NaCl 0.225%, and total parenteral nutrition [TPN]) does not significantly alter total immunoglobulin G concentrations or concentration of antibodies to hepatitis B surface antigen or type III GBS. As well, the in vitro functional activity for type III GBS of the IVIG, when mixed with these solutions for up to 24 hours, remained intact. An apparent decrease in bactericidal killing was seen with the IVIG/central TPN mixture. This apparent decrease was found to be an artifact of the high concentration of glucose (20 percent) in the solution.

CONCLUSIONS

We propose that Gammagard may be mixed with these solutions through Y-site connections without loss of antibody content or functional activity of the IVIG.

The midcycle gonadotropin surge in normal women occurs in the face of an unchanging gonadotropin-releasing hormone pulse frequency

The midcycle gonadotropin surge is a critical event in normal reproductive cycles and requires functional integration of the hypothalamus, pituitary, and ovary. To determine whether a change in GnRH frequency occurs coincident with the onset or termination of the surge in normal women, 20 studies were performed at a sampling interval of every 5 min for up to 36 h. The frequency of pulsatile GnRH secretion was assessed by the use of two surrogate markers of its secretion, LH and free alpha-subunit (FAS). The timing of the studies was prospectively determined by serial ultrasound and previous cycle history, whereas measurements of LH, FSH, estradiol, and progesterone in daily blood samples were used retrospectively to locate the frequent sampling study in relation to the day of ovulation in each individual. The frequent sampling studies were divided into late follicular phase (LFP; days -4 to -2) and early, mid-, and late portions of the midcycle surge (days -1 to 1) in relation to the 95% confidence limits of the LH peak derived from daily samples in 69 normal ovulatory women. The patterns of LH and FAS secretion were pulsatile at all times during the midcycle surge. The amplitude of LH pulsations increased from the LFP and early surge to the midportion of the midcycle surge (5.9 +/- 6 and 15.1 +/- 5 vs. 39.0 +/- 3 IU/L; P < 0.0001) and decreased from the mid- to the late portion of the surge (13.4 +/- 5 IU/L; P < 0.0001). Likewise, the amplitude of FAS pulse increased from the LFP and early surge to the midportion of the surge (82.4 +/- 59 and 153.1 +/- 50 vs. 421.4 +/- 35 ng/L; P < 0.0001) and decreased from the mid- to the late portion of the surge (190.8 +/- 49 ng/L; P < 0.0002). Although there was excellent concordance of pulsatile secretion of LH and FAS, significantly more pulses of FAS were detected than of LH (P < 0.0001). There was no change in frequency (expressed as interpulse interval) between the LFP and the early and midportions of the surge for LH (70.0 +/- 8, 67.5 +/- 7, and 65 +/- 5 min, respectively) or FAS (55.1 +/- 7, 54.6 +/- 6, and 60.0 +/- 4 min). However, there was an increase in LH interpulse interval (decrease in pulse frequency) in the late portion of the surge (87.0 +/- 6 min) compared to the early and midportions of the surge (P < 0.02 and P < 0.0005, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

B-lymphoid to granulocytic switch during hematopoiesis in a transgenic mouse strain

B-lymphoid and myeloid development are markedly perturbed in a unique transgenic mouse strain, max 41. Pro-B, pre-B, and B lymphocytes were severely reduced but granulocytes were greatly elevated. This phenotype could be adoptively transferred with bone marrow cells. It was not alleviated by bcl-2 or myc transgenes that promote lymphocyte survival or proliferation. Bitransgenic myc/max 41 mice developed pre-B cell lymphoma. An accompanying massive granulocytosis unexpectedly proved to be clonally derived from the pre-B lymphoma cells. These observations suggest that B lymphopoiesis in max 41 mice has been diverted to granulocyte production. Since neither cell type expressed the transgene, this novel lymphomyeloid deviation probably reflects insertional alteration of a hematopoietic regulatory gene.

Cranial fractures associated with facial fractures: a review of mechanism, type, and severity of injury

A 100-month retrospective review was undertaken to identify the population characteristics of patients with both facial and cranial fractures and to establish the relationships between them. A 4.4% incidence of cranial fractures was found in the 882 patients with facial fractures. These patients tended to be males (85%) between the ages of 16 and 30 years (54%) who were involved in motor vehicle accidents (64%). Patients with midfacial fractures predominated (70%), and these injuries were most frequently associated with fractures of the frontal (38%), sphenoid (24%), or temporal (22%) bones. No relationship was noted between mandibular fractures and cranial fractures. Midfacial fractures were related to individual cranial bone fractures by sutural attachment. The presence of cranial fractures did not play a role in the development of complications associated with facial fractures.