The levonorgestrel intrauterine system for prevention of endometrial cancer in women with obesity: A cost-effectiveness study

OBJECTIVE

To estimate the cost-effectiveness of the levonorgestrel intrauterine system (LNG-IUS) as an endometrial cancer prevention strategy in women with obesity.

METHODS

A Markov decision-analytic model was used to compare 5 strategies in women with a body mass index of 30 or greater: 1) Usual care 2) LNG-IUS for 5 years 3) LNG-IUS for 7 years 4) LNG-IUS for 5 years, replaced once for a total of 10 years 5) LNG-IUS for 7 years, replaced once for a total of 14 years. Obesity was presumed to be associated with a 3-fold relative risk of endometrial cancer incidence and a 2.65-fold disease-specific mortality. The LNG-IUS was assumed to confer a 50% reduction in cancer incidence over the period of the LNG-IUS insertion. Outcomes were incremental cost-effectiveness ratios, calculated in 2019 Canadian dollars (CAD) per year of life saved. One-way and two-way sensitivity analyses were performed.

RESULTS

The LNG-IUS strategy was considered cost-effective if the cost of the intervention is less than $66,400 CAD ($50,000 US dollars) per year of life saved. The strategy becomes cost-effective if the LNG-IUS is inserted at age 57 (strategy #2), at age 52 for strategy #3, at age 51 for strategy #4 and at age 45 for strategy #5, when compared to usual care. The results are stable to variations in cost but sensitive to the estimated risk reduction of the LNG-IUS and the impact of obesity on endometrial cancer incidence and disease-specific mortality.

CONCLUSION

The LNG-IUS is a cost-effective method of endometrial cancer prevention in women with obesity.

Perioperative outcomes of women with and without class III obesity undergoing hysterectomy for endometrioid endometrial cancer: A population-based study

OBJECTIVE

Population-based data on perioperative complications among women with endometrial cancer and severe obesity are lacking. We evaluated 30-day complication rates among women with and without class III obesity (body mass index ≥ 40 kg/m²) undergoing primary surgical management for endometrioid endometrial cancer (EEC), and how outcomes differed according to surgical approach (open vs. minimally invasive).

METHODS

We performed a retrospective population-based cohort study of women with EEC undergoing hysterectomy in Ontario, Canada, between 2006 and 2015. We evaluated perioperative complications in the whole cohort, and in a 1:1 matched analysis using hard and propensity score matching to ensure similar distributions of patient, tumour, provider and institution-level factors between women with and without class III obesity (identified using a surgical billing code). The primary outcome of interest was the 30-day perioperative complication rate.

RESULTS

12,112 women met inclusion criteria; 2697 (22.3%) had class III obesity. We matched 2320 (86%) women with class III obesity to those without. The composite complication rate was significantly higher among women with class III obesity (23.2% vs. 18.4%, standardized mean difference [SMD] = 0.12), primarily due to wound infection/disruption (12.1% vs. 6.2%). There was no difference in outcomes for women with and without class III obesity when a minimally invasive approach was used.

CONCLUSIONS

Wound infection/disruption was increased for women with class III obesity compared to women without. Otherwise, perioperative complications were similar between the matched pairs. When minimally invasive approaches were used, women with class III obesity had a similar risk of complications as women without obesity.

Impact of a novel prioritization framework on clinician-led oncology drug submissions

Background

In Canada, requests for public reimbursement of cancer drugs are predominately initiated by pharmaceutical manufacturers. Clinician-led submissions provide a mechanism to initiate the drug funding process when industry does not submit a request for funding consideration. Although such requests are resource-intensive to produce, Cancer Care Ontario (cco) has the capacity to facilitate clinician-led submissions. In 2014, cco began developing a cancer drug prioritization framework that allocates resources to systematically address a growing number of clinician-identified funding gaps with clinician-led submissions.

Methods

Cancer site-specific drug advisory committees established by cco consist of health care practitioners whose roles include identifying and prioritizing funding gaps. The committees submit their identified gaps to a cross-cancer-site prioritization exercise in which the requests are ranked based on a set of guiding principles derived from health technology assessment. The requests are then sequentially allocated the resources needed to meet submission requirements. Whether the funding gap is of provincial or pan-Canadian relevance determines where the submission is filed for assessment.

Results

Since its inception, the cco framework has identified 17 funding gaps in 9 cancer sites. In 4 prioritizations, the framework supported 6 submissions. As of June 2018, the framework had contributed to the eventual funding of more than 9 new drug-indication pairs, with more awaiting funding consideration.

Conclusions

The cco prioritization framework has enabled clinicians to effectively and systematically identify, prioritize, and fill funding gaps not addressed by industry. Ultimately, the framework helps to ensure that patients can access evidence-informed and cost-effective therapies. The framework will continue to evolve as it encounters new challenges, including funding requests for rare indications.

Initiating a lymphedema screening program for breast cancer patients: Determining variability as a first step towards standardization

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Background: Breast cancer-related lymphedema (BCRL) is a known morbidity from treatment, and yet published estimates of its incidence are highly variable. Typically, a single volume measurement is recorded and the degree of intra-rater variability undefined. A threshold 5% limb volume change over time is used to define “mild lymphedema.” Therefore, small variations in volume measurements could substantially lead to over or under-diagnosis of BRCL. Gage R&R is a measurement systems analysis tool that quantifies the amount of variability induced in measurements by the measurement system itself and compares this to the total variability observed. The objective of this study was to define the degree of variability in perometer arm volume measurements and factors contributing to this. Methods: A medical assistant (MA) was trained by a certified lymphedema therapist (CLT) to perform perometer-based lymphedema screening in the MD Anderson Nellie B. Connally Breast Center. Three measurements of each arm were taken and intra-rater variability against the mean calculated. Gage R&R testing was performed by the MA and CLT, to determine the degree of repeatability and reproducibility variation. As a part of this analysis, 30 patients had both their left and right arm volume measured 3 times by each measurer. Results: Over 6 months, 565 breast cancer patients had preoperative BCRL screening by the MA, with an overall intra-rater variability of 2.2%. Among the 30 patients in the Gage R&R study, median body mass index (BMI) was 27.7 (range 19.7-38.3), median height 1.61m (range 1.52-1.73m), intrarater variability of the MA was 2.07% and of the CLT was 1.21%. Gage R&R accounted for 4.77% of total variability, 1.26% repeatability and 3.51% reproducibility. Regression analysis demonstrated that patient BMI and height impacted variability in measurements (R2= 16.27). Conclusions: Intra-rater variability for perometer arm measurements diminishes with experience. Gage R&R variability is acceptable per industry standards, but there is room for improvement. Our findings suggest a role for targeted interventions to minimize variability in the diagnosis of BCRL based on patient characteristics.

Intraoperative lymph node evaluation using 18F-FDG and a hand-held gamma probe in endometrial cancer surgery--a pilot study

PURPOSE

The purpose of this pilot study was to assess feasibility, safety, and accuracy of detection of metastatic nodes intraoperatively with a hand-held gamma (PET) probe after administration of 18F-FDG in patients with high risk endometrial cancer (EC).

MATERIALS AND METHODS

This is a prospective, cohort study. Twenty-two patients with clinical Stage I or II EC with high-risk histologic subtypes who were candidates for open surgical intervention were screened for the study. After screening, there were seven study patients (mean age: 64; range: 53-77) who were eligible for the study. In the entire cohort, there were 61 nodal stations that were assessed with a gamma counter intraoperatively, in vivo and again after removal of the node. All adverse events were recorded and operating room staff was monitored for radiation exposure. Resected nodes underwent histological assessment as per routine clinical practice.

RESULTS

Range of maximal counts per second recorded in vivo and ex vivo were 0-86 and 0-17, respectively. Of all the nodes examined, one node was positive for metastatic disease; however, intraoperatively the lymph node readings were not higher than other lymph node basins assessed in same patient. No adverse events were recorded. The surgeons recorded the maximum average radiation exposure of all healthcare personnel with an average exposure of 0.08 mSV per case (range, 0.06-0.15).

CONCLUSION

Use of hand-held gamma probe for intraoperative staging of patients with high risk EC is feasible, safe, and radiation exposure levels for all members of the healthcare team were within radiation safety guidelines. However, its use for detection of lymph node metastases needs further evaluation.

Effect of a new model for multidisciplinary breast cancer care on clinical metrics leading to efficiency and timeliness of access

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Background: The multidisciplinary approach to breast cancer care provides a coordinated mechanism for evaluating and treating new patients. Improving the structure of clinic models may further enhance the delivery of cancer care. Methods: In May 2013, multi-team (MT) clinics were introduced in the breast center at the University of Texas MD Anderson Cancer Center. Local patients with newly diagnosed breast cancer were scheduled to be seen in a MT clinic with testing coordinated for the same day. Patient cases were first reviewed and examined concurrently by physicians from each discipline (surgical, medical, radiation), followed by sequential visits with each clinician for a more detailed discussion. The goal of this program was to determine whether a highly integrated multidisciplinary clinic model would improve the efficient delivery of cancer treatment. Results: From 5/2013 – 5/2014, 211 newly diagnosed and untreated breast cancer patients were seen in the MT clinic. Clinical metrics were reviewed retrospectively and compared to newly diagnosed and untreated patients who entered the clinic using the standard model (non-MT patients) (n=1944). Please see Table for details of the data. Conclusions: Multi-team clinics improved clinical metrics leading to efficiency and timeliness of access. The model enriched for a population of patients who were more likely to receive treatment within the breast center, utilize institutional resources, and enroll into clinical trials. [Table: see text]

Heparin for pregnant women with acquired or inherited thrombophilias

BACKGROUND

Thrombophilias, which are associated with a predisposition to thrombotic events, have been implicated in adverse obstetrical outcomes such as intrauterine growth restriction, stillbirth, severe early onset pre-eclampsia, and placental abruption. Heparin administration in pregnancy may reduce the risk of these events.

OBJECTIVES

The objective of this review was to assess the effects of heparin on pregnancy outcomes for women with a thrombophilia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (July 2002), MEDLINE, EMBASE, CINAHL, Scidex (via OVID Technologies - July 2002) and reference lists and personal files.

SELECTION CRITERIA

Randomized controlled trials comparing heparin with placebo or no treatment, or randomized controlled trials comparing any two treatments. Quasi randomized studies would be included.

DATA COLLECTION AND ANALYSIS

Data would be abstracted from identified studies and recorded on a paper form by two reviewers.

MAIN RESULTS

No studies were included.

REVIEWER'S CONCLUSIONS

There are no completed trials to determine the effects of heparin on pregnancy outcomes for women with a thrombophilia.

Maternal plasma homocysteine levels in women with preterm premature rupture of membranes

Homocysteine is a sulfur-containing amino acid produced by the breakdown of methionine. Plasma homocysteine levels can be elevated due to a variety of genetic and nutritional factors. Poor nutrition from diets low in folate and vitamin B12 can lead to hyperhomocysteinemia. Mildly elevated levels of homocysteine have been implicated in a number of disease processes such as atherosclerotic vascular disease and adverse obstetrical outcomes. High levels of plasma homocysteine are also associated with abnormal collagen cross-linking. Due to homocysteine's effects on connective tissue integrity, it is hypothesized that hyperhomocysteinemia in pregnancy is associated with preterm premature rupture of membranes (PPROM). Hyperhomocysteinemia, therefore, could be a treatable cause of this important public health concern.

The effects of different culture media, glucose, pyridine nucleotides and adenosine on the activity of 11beta-hydroxysteroid dehydrogenase in rat Leydig cells

11Beta-hydroxysteroid dehydrogenase (11betaHSD) reversibly converts glucocorticoids into inert 11-ketosteroids. The direction of the reaction has been found to vary with the cell type and sub-cellular preparation used. We have investigated if the directionality of 11betaHSD can be influenced by the nature of the culture medium and compounds added during incubation of rat testis Leydig cells. We found that when the cells were cultured in Dulbecco's Modified Eagle Medium (DMEM) that the dehydrogenase (11betaDH) activity was higher than the reductase (11KSR) activity (11betaDH:11KSR ratio approximately 2:1). When glucose was omitted from the DMEM a higher 11betaDH:11KSR ratio (approximately 33:1) was obtained. However, when the cells were cultured in a combination of DMEM/Ham's F12 (1:1, v/v), a ninefold increase in 11KSR activity was obtained whereas 11betaDH activity was inhibited by 64% compared with cells incubated in DMEM alone. Consequently, the predominant activity changed from a dehydrogenase to a reductase (11betaDH:11KSR ratio 1:15). Addition of the individual components of the Ham's F12 medium to DMEM showed that only pyruvate and/or the amino acids were able to mimic the effects of DMEM/Ham's F12. Similar differential effects were found when NAD+, NADH or adenosine were added to the Leydig cells incubated in DMEM (three to fivefold increases and 20-50% decreases in 11KSR and 11betaDH activities, respectively). In contrast, NADP+ was found to increase 11betaDH activity (up to threefold) but NADPH had no effect on 11KSR activity. Cells incubated with DMEM/Ham's F12, NAD+, NADP+ and adenosine were found to have higher ATP levels (four to sixfold) than those incubated in DMEM alone. These results illustrate that the relative 11betaDH and 11KSR activities of 11betaHSD in Leydig cells are markedly and differentially altered by the nature of the incubation medium and compounds added.

CD28 is required for germinal center formation

Previous studies have demonstrated that the T cell costimulatory molecule, CD28, is important in the development of humoral immunity. CD28-deficient mice exhibit defects in isotype switching and are more susceptible to pathogens that depend on an effective Ab response. To determine the basis of these defects, we have examined B cell responses of CD28-deficient mice at the microenvironmental level. Early in a normal T-dependent immune response, small numbers of B cells undergo activation in the T cell-rich zone of secondary lymphoid tissues and then migrate to B cell areas. These migrant B cells found developing germinal centers by proliferative expansion, during which individual cells acquire mutations in their rearranged Ig genes. B cell mutants retaining higher affinities for Ag undergo positive selection in germinal centers, resulting in the establishment of the memory B cell compartment. In the present study, we demonstrate that although potentially Ag-reactive cells within the lymphoid follicle accumulate following antigenic challenge, these cells fail to undergo proliferative expansion to form germinal centers and do not acquire somatic mutations in CD28-deficient animals. Thus, the CD28 activation pathway is required for Ab responses to T-dependent Ags. cell compartment. In the present study, we demonstrate that although potentially Ag-reactive cells within the lymphoid follicle accumulate following antigenic challenge, these cells fail to undergo proliferative expansion to form germinal centers and do not acquire somatic mutations in CD28-deficient animals. Thus, the CD28 activation pathway is required for Ab responses to T-dependent Ags.

CD28 is required for germinal center formation

Previous studies have demonstrated that the T cell costimulatory molecule, CD28, is important in the development of humoral immunity. CD28-deficient mice exhibit defects in isotype switching and are more susceptible to pathogens that depend on an effective Ab response. To determine the basis of these defects, we have examined B cell responses of CD28-deficient mice at the microenvironmental level. Early in a normal T-dependent immune response, small numbers of B cells undergo activation in the T cell-rich zone of secondary lymphoid tissues and then migrate to B cell areas. These migrant B cells found developing germinal centers by proliferative expansion, during which individual cells acquire mutations in their rearranged Ig genes. B cell mutants retaining higher affinities for Ag undergo positive selection in germinal centers, resulting in the establishment of the memory B cell compartment. In the present study, we demonstrate that although potentially Ag-reactive cells within the lymphoid follicle accumulate following antigenic challenge, these cells fail to undergo proliferative expansion to form germinal centers and do not acquire somatic mutations in CD28-deficient animals. Thus, the CD28 activation pathway is required for Ab responses to T-dependent Ags. cell compartment. In the present study, we demonstrate that although potentially Ag-reactive cells within the lymphoid follicle accumulate following antigenic challenge, these cells fail to undergo proliferative expansion to form germinal centers and do not acquire somatic mutations in CD28-deficient animals. Thus, the CD28 activation pathway is required for Ab responses to T-dependent Ags.

Regulation of RAG-2 protein expression in avian thymocytes

The recombinase-activating genes, RAG-1 and RAG-2, have been shown to be necessary to initiate the process of V(D)J recombination during the ontogeny of lymphocytes. While much is known about the end products of this rearrangement process, little is known about the function or regulation of the components of the recombinase system. To this end, we have generated a monoclonal antibody to the chicken RAG-2 protein. Chicken thymocytes were found to express high levels of RAG-2, part of which is phosphorylated. Within thymocytes, RAG-2 is expressed primarily within the nucleus. RAG-2 protein levels are high in the CD4- CD8- and CD4+ CD8+ immature thymocytes but absent at the single-positive CD4+ CD8- or CD4- CD8+ stage of thymocyte development. Mitogenic stimulation of thymocytes with phorbol myristate acetate and ionomycin results in down-regulation of RAG-2 expression. Consistent with these data, in vivo levels of RAG-2 are markedly lower in proliferating thymocytes than in smaller, G0/G1 cells. Down-regulation of RAG-2 expression appears to occur before cells enter S phase, suggesting that RAG-2 function may be limited to noncycling cells.

Peripheral B cell maturation. II. Heat-stable antigen(hi) splenic B cells are an immature developmental intermediate in the production of long-lived marrow-derived B cells

HSAhi B cells comprise 5 to 10% of adult mouse splenic B cells and are phenotypically and functionally immature. To assess their origin and relationship to mature, heat-stable Ag (HSA)lo B cells, we determined HSA and surface IgD phenotype among splenic B cells throughout development, as well as during reconstitution of lethally irradiated adults given adult B-depleted bone marrow. In each case, HSAhi splenic B cells predominate during the earliest stages of B cell genesis. Furthermore, 5-bromo-2'-deoxyuridine labeling experiments indicate rapid turnover within both the marrow and peripheral HSAhi pools, and adoptive transfer studies show that peripheral HSAhi splenic B cells differentiate to HSAlo within 4 days. Finally, splenic HSAhi B cells reconstitute both primary and memory humoral responses. Together, these data indicate that splenic B cells in the HSAhi subset are an intermediate maturational stage in the adult periphery.

Peripheral B cell maturation. II. Heat-stable antigen(hi) splenic B cells are an immature developmental intermediate in the production of long-lived marrow-derived B cells

HSAhi B cells comprise 5 to 10% of adult mouse splenic B cells and are phenotypically and functionally immature. To assess their origin and relationship to mature, heat-stable Ag (HSA)lo B cells, we determined HSA and surface IgD phenotype among splenic B cells throughout development, as well as during reconstitution of lethally irradiated adults given adult B-depleted bone marrow. In each case, HSAhi splenic B cells predominate during the earliest stages of B cell genesis. Furthermore, 5-bromo-2'-deoxyuridine labeling experiments indicate rapid turnover within both the marrow and peripheral HSAhi pools, and adoptive transfer studies show that peripheral HSAhi splenic B cells differentiate to HSAlo within 4 days. Finally, splenic HSAhi B cells reconstitute both primary and memory humoral responses. Together, these data indicate that splenic B cells in the HSAhi subset are an intermediate maturational stage in the adult periphery.

Arachidonic acid metabolism in cells transfected with sense and anti-sense cDNA to annexin I

Thymic epithelial cell line TEA3A1 produce prostaglandin E2 (PGE2) and express high levels of annexin I. In order to study the relationship between the levels of annexin I expression and the arachidonic acid metabolism, TEA3A1 cells transfected with expression vector containing full length annexin I cDNA in either sense or anti-sense orientation was studied. In the anti-sense cells where the level of annexin I was reduced, the PGE2 production was significantly lower. On the other hand, PGE2 production was significantly higher in sense cells where the production of annexin I was also higher than in control cells. Our results show that increased PGE2 production in sense cells was accompanied by higher levels of PLA2 enzymatic activities. These results suggest that the production of annexin I is positively associated with the phospholipase A2 enzymatic activity and the prostaglandin production in thymic epithelial cells.

Peripheral B cell maturation. I. Immature peripheral B cells in adults are heat-stable antigenhi and exhibit unique signaling characteristics

Whether recently generated peripheral B cells in adults are functionally equivalent to immature B cells in the neonatal spleen is unknown. We have identified a splenic B cell subpopulation in adults whose phenotypic and in vitro characteristics closely resemble those of neonatal B cells. These cells are defined by the cell surface phenotype heat-stable Aghi (HSAhi), and make up 10 to 15% of the adult splenic B cell pool. HSAhi B cells in adults bear the immature phenotype B220lo sIgMhi, and are 50% sIgD+. Furthermore, after sublethal irradiation, the initial wave of newly generated splenic B cells in self-reconstituting adults express a similar phenotype. In keeping with previous data on neonatal B cells, HSAhi cells from either normal or self-reconstituting mice are refractory to stimulation with anti-IgM antibodies, yet proliferate upon LPS stimulation, and generate primary antibody responses if given appropriate T cell help. In contrast to neonatal cells, HSAhi adult B cells are refractory to stimulation with PMA plus ionomycin. Together, these data suggest that peripheral HSAhi B cells in adults correspond to recently generated B cells, whose signaling characteristics are distinct from previously described B cell subsets.

Peripheral B cell maturation. I. Immature peripheral B cells in adults are heat-stable antigenhi and exhibit unique signaling characteristics

Whether recently generated peripheral B cells in adults are functionally equivalent to immature B cells in the neonatal spleen is unknown. We have identified a splenic B cell subpopulation in adults whose phenotypic and in vitro characteristics closely resemble those of neonatal B cells. These cells are defined by the cell surface phenotype heat-stable Aghi (HSAhi), and make up 10 to 15% of the adult splenic B cell pool. HSAhi B cells in adults bear the immature phenotype B220lo sIgMhi, and are 50% sIgD+. Furthermore, after sublethal irradiation, the initial wave of newly generated splenic B cells in self-reconstituting adults express a similar phenotype. In keeping with previous data on neonatal B cells, HSAhi cells from either normal or self-reconstituting mice are refractory to stimulation with anti-IgM antibodies, yet proliferate upon LPS stimulation, and generate primary antibody responses if given appropriate T cell help. In contrast to neonatal cells, HSAhi adult B cells are refractory to stimulation with PMA plus ionomycin. Together, these data suggest that peripheral HSAhi B cells in adults correspond to recently generated B cells, whose signaling characteristics are distinct from previously described B cell subsets.

Layered collagen fabric of cerebral aneurysms quantitatively assessed by the universal stage and polarized light microscopy

We evaluated the effectiveness of the Universal stage, an instrument for measuring three-dimensional orientation of birefringent materials, for studying the collagen fabric in the wall of brain aneurysms. Vessels from autopsy were fixed at normal arterial distending pressure with 10% formalin, and prepared for polarized light microscopy, with paraffin embedding and staining with picrosirius red for birefringent enhancement. Quantitative data were obtained from tangential and oblique sections (7 microns thickness) of an intact 8 mm aneurysm, a 1.5 mm aneurysm, and a tangential section (3 microns thickness) of a cerebral artery. Sections of full-size aneurysms seen through the microscope, adjusted either for plane or circularly polarized light, revealed distinctive layers of collagen across the aneurysmal wall, which at higher magnification were further subdivided. Three-dimensional measurements, numbering 1,082, were made by use of the Universal stage attachment to the polarizing microscope. They were plotted by computer-controlled graphics on Lambert projections and analyzed by circular statistics. When assessed layer by layer, the collagen spanned a full range of orientations relative to the tangential plane. The circular standard deviation, a measure of the spread of alignment about the mean, was as low as 10 degrees for coherently organized collagen and as high as 40 degrees for the least coherently organized collagen, values characteristic of either the organized tunica media, or the least organized tunica adventitia of cerebral arteries. Although there was a marked thinning of the wall of one aneurysm, there was no evidence of structural weakness based only on the directional organization assessed by our measurements.

Analysis of a novel VHS107 haplotype in CLA-2 and WSA mice. Evidence for gene conversion among IgVH genes in outbred populations

Gene conversion has been suggested as the basis for many VH allelic differences, particularly in the murine VHS107 family. Whether conversion among IgVH genes is likely to have occurred in outbred populations has not been directly addressed. The CLA-2/Cn and WSA strains, which were recently and independently derived from a feral population exhibiting low responsiveness to PC, provide the opportunity to approach this question. In previous studies, the heavy chain cDNA sequence of a PC-specific hybridoma derived from CLA-2/Cn suggested gene conversion events within the VHS107 family. Accordingly, we have examined the germline VHS107 genes of CLA-2/Cn and WSA. The results indicate that: (a) The CLA-2 and WSA strains bear an identical but novel VHS107 family haplotype, which lacks a V3 element and contains a V1, a V13, and two V11 genes; (b) low PC responsiveness in these populations is unlikely due to an inability to express the V1 member of the VHS107 gene family; and (c) when compared with the other known VHS107 haplotypes, the proportion of differences consistent with gene conversion greatly exceeds that expected by random base substitution. Thus, gene conversion events appear to have occurred with considerable frequency in the evolution of the murine VHS107 family, especially among the V3, V13, and V11 members.

Probing the cellular basis for immunologic memory: approaching functional distinctions between primed and unprimed B-cell populations

The physiologic distinctions between secondary and primary lymphoid populations remain largely conceptual. Altered activation, differentiation, and compartmentalization properties likely underlie these differences, but little precise knowledge of how these parameters are affected by antigen priming exists. Because lymphoid populations are dynamic entities and priming is a temporal process, lineage and life span analyses of definable subpopulations are required for the design and interpretation of experiments to probe functional distinctions between primed versus unprimed B-cell populations. Subsequent studies, which address differences in activation requirements and collaborative potential of primed versus unprimed B-cells are further required to evaluate the cellular basis of immunologic memory. Recent advances in the ability to dissect lymphoid differentiation subsets and lineages, coupled with a rapidly expanding knowledge of molecules which mediate B-lymphocyte growth and differentiation, render these possibilities amenable to experimental analysis.

Interaction and sequence diversity among T15 VH genes in CBA/J mice

Nucleotide sequences of the four genes composing the T15 heavy chain variable region (VH) family of the CBA/J mouse have been determined. Comparison of these sequences with their published BALB/c and C57BL/10 homologues reveals that nucleotide differences found between given alleles of two strains, i.e., CBA/J and BALB/c, are observed in other family members of the same strain. We suggest that these patterns of sequence variation are most readily explained by gene interaction (conversion). Additionally, the sequence of a CBA/J hybridoma, 6G6, proposed to have been generated by gene conversion, is directly encoded by the CBA/J V11 gene indicating that the putative conversion has occurred meiotically in the germline. These results are consistent with the premise that gene correction is occurring frequently among members of this family and that such processes may contribute significantly to the evolution of Ig variable region genes even in the relatively short time frame of inbred strain derivation.

Properties of porcine liver and testicular steroid sulphotransferases: reaction conditions and influence of naturally occurring steroids and steroid sulphates

Sulphotransferase activity has been assayed in porcine liver and testis cytosol using either 3'-phosphoadenosine-5'-phospho [35S]sulphate (PAPS) or unlabelled PAPS as sulphate donors. In porcine liver the sulphotransferase for DHA was linear for up to 10 min, the optimum pH was 7.7 and optimum temperature, 37 degrees C. The apparent Km value was found to be 91 mumol/l and the activity was inhibited non-competitively by 5 alpha-androst-16-en-3 beta-yl sulphate, with all concentrations used (0.02-25 mumol/l) inhibiting the enzyme to the same extent. Time courses for sulphoconjugation of pregnenolone and 5 alpha-androst-16-en-3 beta-ol were linear for up to at least 10 min or up to only 5 min, respectively. The optimum pH values and temperatures were pH 8.0 and 37 degrees C in each case. The porcine testicular sulphotransferase activity for DHA as substrate was linear with time up to 10 min, the apparent Km for the reaction was 2 mumol/l and apparent Vmax 10 nmol/l/mg/min. 5 alpha-Androst-16-en-3 beta-yl sulphate (11.3-45.2 mumol/l) failed to inhibit the enzyme activity. The time-course for the reaction, when pregnenolone was used as substrate, was also linear up to 10 min at the optimum pH 8.0 but, in contrast to the reaction when DHA was the substrate, had an apparent Km of 20 mumol/l and was inhibited by pregnenolone sulphate, 5 alpha-androst-16-en-3 beta-yl sulphate, DHA and 5 alpha-androst-16-en-3 beta-ol, but not by DHA sulphate. 5 alpha-Androst-16-en-3 beta-yl sulphate inhibited the reaction non-competitively and to the same extent at concentrations over the range 11.3-45.2 mumol/l. These data suggest that DHA and pregnenolone may not be sulphoconjugated by the same sulphotransferase. With 5 alpha-androst-16-en-3 beta-ol as substrate, the time-course for its sulphate formation was linear up to 15 min, and this reaction could explain the quantities of 5 alpha-androst-16-en-3 beta-yl sulphate that are found endogenously in porcine testis. Our results further suggest that these quantities could well inhibit the sulphation of pregnenolone in porcine testis in vivo, and the possibility of control of sulphoconjugation in this tissue is discussed. Having regard to the smaller quantities of 5 alpha-androst-16-en-3 beta-yl sulphate present in porcine liver, our results suggest that the sulphation of DHA there may not be so much affected.

Sulphoconjugation of steroids in porcine liver. Partial purification of the cytosolic sulphotransferases for pregnenolone and 5 alpha-androst-16-en-3 beta-ol

Steroid sulphotransferase activities for 5 alpha-androst-16-en-3 beta-ol and pregnenolone in porcine liver cytosol have been assayed using 3'-phosphoadenosine-5'-phospho[35S]sulphate as sulphate donor. 5 alpha-Androst-16-en-3 beta-ol sulphotransferase activity was obtained from porcine liver cytosol by gel filtration chromatography; activity was linear with time up to about 5 min., the optimum pH was near 8.0 and optimum temperature 37 degrees C. Pregnenolone sulphotransferase activity was partially purified from porcine liver cytosol using DEAE-cellulose chromatography with an ionic gradient of KC1. This enzyme activity was linear with time up to 10 min and had optimum pH and temperature of 8.0 and 37 degrees C, respectively.