Clinical Trials in Veterinary Medicine: A New Era Brings New Challenges

Randomized clinical trials (RCTs) are among the most rigorous ways to determine the causal relationship between an intervention and important clinical outcome. Their use in veterinary medicine has become increasingly common, and as is often the case, with progress comes new challenges. Randomized clinical trials yield important answers, but results from these studies can be unhelpful or even misleading unless the study design and reporting are carried out with care. Herein, we offer some perspective on several emerging challenges associated with RCTs, including use of composite endpoints, the reporting of different forms of risk, analysis in the presence of missing data, and issues of reporting and safety assessment. These topics are explored in the context of previously reported veterinary internal medicine studies as well as through illustrative examples with hypothetical data sets. Moreover, many insights germane to RCTs in veterinary internal medicine can be drawn from the wealth of experience with RCTs in the human medical field. A better understanding of the issues presented here can help improve the design, interpretation, and reporting of veterinary RCTs.

Mortality among patients with pulmonary non-tuberculous mycobacteria disease

SETTING

Tertiary referral center, National Institutes of Health (NIH), USA.

OBJECTIVE

To estimate the mortality rate and its correlates among persons with pulmonary non-tuberculous mycobacteria (PNTM) disease.

DESIGN

A retrospective review of 106 patients who were treated at the NIH Clinical Center and met American Thoracic Society/Infectious Diseases Society of America criteria for PNTM. Eligible patients were aged ⩾18 years and did not have cystic fibrosis or human immunodeficiency virus (HIV) infection.

RESULTS

Of 106 patients followed for a median of 4.9 years, 27 (25%) died during follow-up, for a mortality rate of 4.2 per 100 person-years. The population was predominantly female (88%) and White (88%), with infrequent comorbidities. Fibrocavitary disease (adjusted hazard ratio [aHR] 3.3, 95% confidence interval [CI] 1.3-8.3) and pulmonary hypertension (aHR 2.1, 95%CI 0.9-5.1) were associated with a significantly elevated risk of mortality in survival analysis.

CONCLUSIONS

PNTM remains a serious public health concern, with a consistently elevated mortality rate across multiple populations. Significant risk factors for death include fibrocavitary disease and pulmonary hypertension. Further research is needed to more specifically identify clinical and microbiologic factors that jointly influence disease outcome.

Therapeutic drug monitoring of posaconazole oral suspension in paediatric patients younger than 13 years of age: a retrospective analysis and literature review

WHAT IS KNOWN AND OBJECTIVE

Posaconazole is an extended-spectrum triazole antifungal with activity against a variety of clinically significant yeasts and moulds. Posaconazole is not currently approved by the U.S. Food and Drug Administration for use in children younger than 13 years of age. Our primary objective was to describe the dosing and observed trough concentrations with posaconazole oral suspension in paediatric patients at the National Institutes of Health Clinical Center (Bethesda, MD).

METHODS

This retrospective single-centre study reviewed paediatric patients younger than 13 years of age initiated on posaconazole oral suspension. Patients were included if they were initiated on posaconazole for prophylaxis or treatment for fungal infections from September 2006 through March 2013 with at least one trough concentration collected after at least 7 days of therapy.

RESULTS AND DISCUSSION

A total of 20 male patients were included, of whom 15 (75%) had chronic granulomatous disease. The median age of patients was 6·5 years (range: 2·8-10·7). A total of 79 posaconazole trough concentrations were measured in patients receiving posaconazole as prophylaxis (n = 8) or treatment (n = 12). Posaconazole dose referenced to total body weight ranged from 10·0 to 49·2 mg/kg/day. Posaconazole trough concentrations ranged from undetectable (<50 ng/mL) up to 3620 ng/mL and were ≥500, ≥700 and ≥1250 ng/mL in 95%, 60% and 25% of patients, respectively.

WHAT IS NEW AND CONCLUSIONS

Patients younger than 13 years of age had highly variable trough concentrations, and recommendations for the appropriate dosing of posaconazole oral suspension remain challenging. Until studies are conducted to determine the appropriate dosing of posaconazole in this patient population, therapeutic drug monitoring should be considered to ensure adequate posaconazole exposure.

Randomised controlled trial of alternative messages to increase enrolment in a healthy food programme among individuals with diabetes

OBJECTIVES

We compared the effectiveness of diabetes-focused messaging strategies at increasing enrolment in a healthy food programme among adults with diabetes.

METHODS

Vitality is a multifaceted wellness benefit available to members of Discovery Health, a South Africa-based health insurer. One of the largest Vitality programmes is HealthyFood (HF), an incentive-based programme designed to encourage healthier diets by providing up to 25% cashback on healthy food purchases. We randomised adults with type 2 diabetes to 1 of 5 arms: (1) control, (2) a diabetes-specific message, (3) a message with a recommendation of HF written from the perspective of a HF member with diabetes, (4) a message containing a physician's recommendation of HF, or (5) the diabetes-specific message from arm 2 paired with an 'enhanced active choice'(EAC). In an EAC, readers are asked to make an immediate choice (in this case, to enrol or not enrol); the pros and cons associated with the preferred and non-preferred options are highlighted. HF enrolment was assessed 1 month following the first emailed message.

RESULTS

We randomised 3906 members. After excluding those who enrolled in HF or departed from the Vitality programme before the first intervention email, 3665 (94%) were included in a modified intent-to-treat analysis. All 4 experimental arms had significantly higher HF enrolment rates compared with control (p<0.0001 for all comparisons). When comparing experimental arms, the diabetes-specific message with the EAC had a significantly higher enrolment rate (12.6%) than the diabetes-specific message alone (7.6%, p=0.0016).

CONCLUSIONS

Messages focused on diabetes were effective at increasing enrolment in a healthy food programme. The addition of a framed active choice to a message significantly raised enrolment rates in this population. These findings suggest that simple, low-cost interventions can enhance enrolment in health promoting programmes and also be pragmatically tested within those programmes.

TRIAL REGISTRATION NUMBER

NCT02462057.

Frequency of adverse reactions to first- and second-line anti-tuberculosis chemotherapy in a Korean cohort

OBJECTIVE

To determine the frequency of and risk factors for major adverse drug reactions (MADRs) associated with anti-tuberculosis treatment at a tuberculosis (TB) referral hospital in the Republic of Korea.

METHODS

Data from an ongoing natural history cohort study were analyzed for permanent regimen changes due to adverse drug reactions and confirmed by chart review.

RESULTS

Among 655 subjects, there were 132 MADRs in 112 (17%) subjects. The most common MADRs were gastrointestinal (n = 53), musculoskeletal (n = 22), psychiatric (n = 10), visual (n = 9) and peripheral neuropathic (n = 8). MADRs were more frequent in subjects being treated with second-line regimens (16%) compared to first-line regimens (2.5%). Drugs frequently associated with MADRs were amikacin (3/10, 30%), linezolid (8/29, 28%), para-aminosalicylic acid (47/192, 24%), pyrazinamide (31/528, 5.8%), macrolides (2/44, 4.5%) and cycloserine (12/272, 4.4%). Fluoroquinolones accounted for a single MADR (1/377, 0.003%), despite widespread usage. In multivariate analysis, infection with multi- or extensively drug-resistant disease and previous history of anti-tuberculosis treatment were risk factors for MADR, with adjusted hazard ratios of respectively 2.2 (P = 0.02) and 1.6 (P = 0.04).

CONCLUSION

MADRs are common during anti-tuberculosis chemotherapy in this population, occurring in more than one in six subjects. New and less toxic agents to treat drug-resistant TB are urgently needed.

Differentially androgen-modulated genes in ovarian epithelial cells from BRCA mutation carriers and control patients predict ovarian cancer survival and disease progression

Epidemiological studies have implicated androgens in the etiology and progression of epithelial ovarian cancer. We previously reported that some androgen responses were dysregulated in malignant ovarian epithelial cells relative to control, non-malignant ovarian surface epithelial (OSE) cells. Moreover, dysregulated androgen responses were observed in OSE cells derived from patients with germline BRCA-1 or -2 mutations (OSEb), which account for the majority of familial ovarian cancer predisposition, and such altered responses may be involved in ovarian carcinogenesis or progression. In the present study, gene expression profiling using cDNA microarrays identified 17 genes differentially expressed in response to continuous androgen exposure in OSEb cells and ovarian cancer cells as compared to OSE cells derived from control patients. A subset of these differentially affected genes was selected and verified by quantitative real-time reverse transcription-polymerase chain reaction. Six of the gene products mapped to the OPHID protein-protein interaction database, and five were networked within two interacting partners. Basic leucine zipper transcription factor 2 (BACH2) and acetylcholinesterase (ACHE), which were upregulated by androgen in OSEb cells relative to OSE cells, were further investigated using an ovarian cancer tissue microarray from a separate set of 149 clinical samples. Both cytoplasmic ACHE and BACH2 immunostaining were significantly increased in ovarian cancer relative to benign cases. High levels of cytoplasmic ACHE staining correlated with decreased survival, whereas nuclear BACH2 staining correlated with decreased time to disease recurrence. The finding that products of genes differentially responsive to androgen in OSEb cells may predict survival and disease progression supports a role for altered androgen effects in ovarian cancer. In addition to BACH2 and ACHE, this study highlights a set of potentially functionally related genes for further investigation in ovarian cancer.

Histopathologic features of genetically determined ovarian cancer

Inheritance of germline mutations of BRCA1 or BRCA2 genes account for approximately 10% of ovarian carcinomas, but the characterization of these genetically determined cancers is incomplete. The objective of our study was to characterize the histologic features of ovarian carcinomas associated with germline mutations of BRCA1 and BRCA2. Thirty-two ovarian carcinomas associated with germline BRCA1 or BRCA2 mutations and 40 ovarian carcinomas from patients screened as negative for germline mutations were obtained from three centers. A gynecologic pathologist, blinded to mutation status, reviewed each case, with documentation of the histologic type, Gynecologic Oncology Group (GOG) grade, architectural and nuclear grade, Silverberg grade, and mitotic activity. All BRCA1 and BRCA2 mutation-associated cases were invasive serous carcinomas, and of these 50% were GOG grade 3, 41% had an architectural grade of 3 (predominant solid architecture), 84% a nuclear grade of 3, 72% a mitotic score of 3 (>25 mitoses per 10 HPF), and 75% a Silverberg grade of 3. The differences in histologic type (p = 0.001) and Silverberg grade (p = 0.002) between these tumors and the control group were statistically significant and remained so when comparisons between BRCA carriers and noncarriers were restricted to carcinomas of serous histology alone. Ovarian carcinomas associated with germline mutations of BRCA1/BRCA2 are, in this study, invasive serous carcinomas, with a statistically significant higher histologic grade than ovarian carcinomas without BRCA mutations when using the recently proposed Silverberg grading system.

Sympathetic and parasympathetic regulation of cystatin S gene expression

The autonomic nervous system plays a regulatory role in the differentiation and growth of salivary glands, and in the expression of salivary specific genes. Cystatin S, a member of the evolutionarily conserved family 2 of the cysteine proteinase inhibitor superfamily, expressed in submandibular and parotid glands of rats during development, can be induced in adults by the beta-adrenergic agonist isopreterenol (IPR). It was shown previously that unilateral sympathectomy or bilateral parasympathectomy reduces IPR-induced cystatin S expression. The present experiments demonstrate that IPR-induced cystatin S gene expression in submandibular glands is reduced as early as 3 days post bilateral denervation of both branches of the autonomic nervous system. The reduction is nearly equal to that of either sympathectomy or parasympathectomy alone, suggesting that factor(s) in both sympathetic and parasympathetic fibers are simultaneously required for IPR-induced cystatin S gene expression.

Activation of androgen receptor-associated protein 70 (ARA70) mRNA expression in ovarian cancer

OBJECTIVE

Androgens have been implicated in ovarian cancer and androgen receptor expression has been reported in 70-95% of ovarian adenocarcinomas, implying a role in ovarian cancer cell biology. Androgen receptor-associated protein 70 (ARA70) is a reported androgen receptor coactivator that enhances the transactivational potential of the androgen receptor up to 10-fold. Because ARA70 expression could amplify androgen action in ovarian cancer cells, we examined patient samples of ovarian cancer for ARA70 expression.

METHODS

Twenty invasive ovarian carcinomas and four nonmalignant ovaries were tested for ARA70 mRNA expression by in situ hybridization using a 35S-labeled riboprobe.

RESULTS

The probe was first assessed using a sample of human benign prostatic hyperplasia. Expression was restricted to cells within the epithelial glands, which are known to express the highest levels of androgen receptor. In the nonmalignant ovary, ARA70 mRNA was expressed in moderate levels in thecal cells associated with antral follicles, with less labeling observed in granulosa cells and stroma. The surface epithelium was negative for ARA70 transcripts, with only low levels observed in occasional cells. In contrast, a high level of ARA70 expression was observed in 17 of the 20 ovarian carcinomas of various histological types. Labeling was associated with the tumor cells while little if any ARA70 mRNA was observed in stromal cells associated with the carcinoma.

CONCLUSION

These observations indicate that ARA70 expression is activated in invasive ovarian cancer tumor cells, and suggest that amplification of androgen action by ARA70 may be involved in the etiology/progression of this disease.

Effect of sympathetic innervation on isoproterenol-induced cystatin S gene expression in rat submandibular glands during early development

The rat submandibular gland is innervated by both sympathetic and parasympathetic branches of the autonomic nervous system which, in turn, regulate the secretory function of the gland. Parasympathetic innervation of rat submandibular glands is present at birth; in contrast, sympathetic innervation reaches the glands by postnatal day 5. Isoproterenol (IPR), a beta-adrenoreceptor agonist, induces hypertrophic and hyperplastic enlargement of rat salivary glands, and induces the expression of a number of genes, including cystatin S (Cys S), a member of family 2 of the cysteine proteinase inhibitor superfamily. Cys S gene expression is tissue specific, cell type specific, occurs temporally during normal development and is not observed in adult animals unless stimulated by IPR. In addition, sympathectomy of adult rat submandibular glands reduced IPR-induced expression of the Cys S gene. This paper reports experiments analyzing the participation of the sympathetic branch of the autonomic nervous system in IPR-induced expression of the cystatin S gene during early development of the submandibular gland. The rat Cys S gene could be induced by IPR by day 3, and the level of Cys S mRNA remained constant until 8 days at which time a dramatic IPR induction of Cys S mRNA was observed. This statistically significant increase in Cys S mRNA at 8 days was diminished, but not completely suppressed, upon sympathectomy of 1-day-old animals. These data indicate that an intact sympathetic innervation is not a requisite for IPR-induced Cys S gene expression in developing submandibular glands; however, sympathetic innervation is required for the full IPR response of the Cys S gene in developing submandibular glands. The developmental experiments presented in this paper indicate that factor(s) coming from the sympathetic nervous system participate in IPR-induced expression of the Cys S gene in rat submandibular glands.

Autonomic regulation of cystatin S gene expression in rat submandibular glands

Innervation of rat submandibular and parotid glands by the autonomic nervous system regulates saliva volume, its rate of secretion and its composition. The autonomic nervous system also plays a regulatory role in the differentiation and growth of salivary glands, and in the expression of specific sets of genes. Rat cystatin S, a member of family 2 of the cysteine proteinase inhibitor superfamily, is expressed in submandibular and parotid glands of human and rat. In the rat, cystatin S gene expression is tissue- and cell type-specific, is temporally regulated during postnatal development, and not observed in adult animals. The beta-adrenergic agonist isoproterenol (IPR) induces hypertrophic and hyperplastic enlargements of rat salivary glands and the expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block, IPR-induced expression of the cystatin S gene in submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in its regulation. Bilateral parasympathectomy also reduces IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Experiments described in this paper suggest that similar factor(s) arising from both the sympathetic and parasympathetic branches of the autonomic nervous system simultaneously participate in IPR-induced cystatin S gene expression in submandibular glands.

Cervical disease in women referred to colposcopy following inadequate smears

The aim of this audit was to determine if inadequate cervical smears are associated with significant cervical pathology. Case records for 52 women with three consecutive inadequate smears referred for colposcopy to the Leicester Royal Infirmary (LRI) were retrieved. Sixteen women underwent large loop excision of the transformation zone (LLETZ) and cervical intraepithelial neoplasia (CIN) was identified in six cases. There were no cases of inadequate smears initiating the diagnosis in 100 consecutive women with invasive cervical cancer. Inadequate smears are associated with high rates of treatment for a low yield of CIN. To reduce morbidity associated with colposcopy it may be acceptable to repeat an inadequate smear after 6 months rather than arranging immediate recall.

Activation of SPARC expression in reactive stroma associated with human epithelial ovarian cancer

OBJECTIVE

SPARC (secreted protein, acidic, rich in cysteine) is a calcium-binding counteradhesive glycoprotein that has the potential to play an important role in promoting tumor progression and invasiveness. SPARC has been reported to be markedly down-regulated in ovarian carcinomas relative to the normal surface epithelium and has been suggested to act as a tumor suppressor in ovarian cancer. To more precisely define potential changes in SPARC expression associated with malignant transformation of the ovary, we compared the distribution of SPARC mRNA and protein expression in patient specimens of malignant and nonmalignant ovaries.

METHOD

SPARC mRNA and protein expression was examined in 24 human invasive ovarian cancers, 5 tumors of low malignant potential (LMP), and 8 nonmalignant ovaries by in situ hybridization and immunohistochemistry.

RESULTS

In nonmalignant ovaries, SPARC mRNA expression was restricted to thecal and granulosa cells of vessiculated follicles. Cytoplasmic SPARC immunoreactivity was observed in these compartments, whereas variable SPARC immunostaining was observed in normal surface epithelial cells. In contrast, high-level expression of SPARC mRNA and protein was detected in stroma of ovaries containing malignant tumor cells, particularly at the tumor-stromal interface of the invading tumors. Lower levels and a more diffuse pattern of SPARC mRNA expression were associated with LMP specimens. SPARC mRNA was not expressed by ovarian adenocarcinoma or by surface epithelial cells. Consistent with the in situ hybridization data, SPARC immunoreactivity was found throughout the reactive stroma of specimens containing ovarian carcinoma. However, despite the lack of detectable SPARC mRNA, SPARC immunoreactivity was consistently observed within the cytoplasm of cancer cells.

CONCLUSION

The pattern of SPARC expression shown in this study indicates that SPARC is up-regulated in reactive stroma associated with invasive ovarian cancer. Moreover, these results raise the possibility that SPARC secreted from the stroma is internalized by ovarian cancer cells and may exert important intracellular effects upon these cells.

The 5'-flanking sequence and regulatory elements of the cystatin S gene

The gene encoding rat cystatin S (Cys S), a salivary gland-specific secretory protein, has CAAT and TATA boxes upstream of the inititation codon (Cox and Shaw, 1992), and contains regions that resemble those of other hormonally responsive eukaryotic genes. The 5'-flanking sequence of the rat Cys S gene has a potential CREB/AP-1 binding site (Rupp et al., 1990; Trejo et al., 1992), two potential glucocorticoid responsive elements (GREs, Drouin et al., 1989), and a possible GR/PR (glucocorticoid/progesterone) responsive element (Forman and Samuels, 1990). One of these potential GREs is adjacent to a potential AP-2 binding site, and another is typical of the glucocorticoid and progesterone receptor binding site. In this report, we have identified three regions in the 5'-flanking region of the Cys S gene that are found in salivary gland-specific genes (Ting et al., 1992) with a GT-rich region located between conserved elements II and III. Transfection experiments described in this paper suggest that a 281-bp DNA fragment from the Cys S gene promoter region with conserved elements II and III, the GT-rich region, and a possible GR/PR responsive element contains a negative regulatory element. In addition, our experiments suggest that the GT-rich region by itself is acting as a positive regulatory element.

Accumulation of p53 protein is frequent in ovarian cancers associated with BRCA1 and BRCA2 germline mutations

BACKGROUND

Mutations in the BRCA1 or BRCA2 genes are responsible for up to 95% of hereditary ovarian cancer cases. Both genes function as tumour suppressor genes, and development of a cancer is thought to require an accumulation of somatic genetic events in addition to the inherited germline predisposition. It is unknown whether these somatic events in BRCA associated ovarian cancer are similar to or distinct from those in sporadic cases. The most frequent somatic genetic event in ovarian cancer is a mutation of the p53 gene.

AIM

To study the role of p53 in hereditary ovarian cancer, by analysing accumulation of the p53 protein in ovarian cancers which occurred in BRCA1 or BRCA2 germline mutation carriers and comparing the results with a panel of ovarian cancers from patients who tested negative for both BRCA1 and BRCA2.

METHODS

The study group consisted of 39 ovarian cancer patients in whom a BRCA mutation had been confirmed previously. p53 Immunohistochemistry was performed on archival tissue using a standard microwave antigen retrieval technique. The rate of p53 accumulation was compared with 40 ovarian cancer cases who tested negative for BRCA1 and BRCA2 germline mutations.

RESULTS

P53 Accumulation was similar in BRCA related ovarian cancers and BRCA negative controls. Overall 27 of 39 BRCA1 or BRCA2 positive cases (69%) had evidence of p53 accumulation, compared with 24 of 40 invasive ovarian cancer cases (60%) which tested negative for BRCA1 and BRCA2 germline mutations. BRCA1 related ovarian cancers showed p53 accumulation in 22 of 30 cases (73%); p53 accumulation was present in five of nine BRCA2 related ovarian cancers.

CONCLUSIONS

In addition to germline BRCA1 and BRCA2 mutations, somatic p53 alterations leading to p53 accumulation are an important event in hereditary ovarian cancer and are as frequent as in non-BRCA-related ovarian cancer.

Differences between hereditary and sporadic ovarian cancer

Approximately 5% of ovarian cancer cases can be attributed to an autosomal dominant inheritance factor. The majority of these cases are due to germline mutations in the BRCA1 or BRCA2 tumoursupressor genes. Patients with hereditary disease do not exhibit pathognomonic features that would allow distinction from non-hereditary (sporadic) cases of ovarian cancer. Our studies are aimed at identifying clinical, histopathological as well as molecular genetic differences between hereditary and sporadic ovarian cancer. Clinical studies of the ovarian cancer cases in 31 families revealed differences regarding age at onset and stage as well as in survival compared with cancer registry controls. The molecular studies of hereditary ovarian cancer are still underway and some preliminary data is discussed.

Borderline malignant change in recurrent müllerian papilloma of the vagina

Malignant change occurred in a benign, recurrent vaginal müllerian polyp. The patient, a 49 year old woman with cerebral palsy, presented with a polypoid mass in the vagina. At four years of age she had presented with a haemorrhagic polyp, and over the following years she had recurrent irregular bleeding and regrowth of the polypoidal mass, requiring a total of 10 operations to excise the polyp. Histological examination of the specimen showed typical müllerian features with tubal, endometrioid, and endocervical cell types. There were significantly abnormal nuclei, indicating low grade or borderline malignancy. Review of previous biopsies showed similar müllerian features but no atypia. This is the first reported case of borderline malignant change in a previously benign recurrent müllerian papilloma of the vagina. Definitive radical surgery or radiotherapy is contraindicated in this patient and she remains under follow up.

Isoproterenol-induced expression of the cystatin S gene in submandibular glands of parasympathectomized rats

Parasympathetic innervation of rat submandibular and parotid glands regulates saliva volume, its rate of secretion and its composition. It also has a regulatory role in hypertrophy and hyperplasia of salivary glands, and in the expression of specific sets of genes. Rat cystatin S is a member of family 2 of the cysteine proteinase inhibitor superfamily. Cystatin S gene expression is tissue- and cell type-specific, temporally regulated during postnatal development, and not observed in adult animals. Isoproterenol (IPR), a beta-adrenergic agonist, induces hypertrophic and hyperplastic enlargement of rat salivary glands and expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block IPR-induced expression of the cystatin S gene in the submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in this regulation. Since both sympathetic and parasympathetic branches of the autonomic nervous system act in parallel in the submandibular gland, it is possible that parasympathetic nerve terminals also provide factor(s) that play a role in regulation of cystatin S gene expression. Experiments described in this paper were designed to test the hypothesis that the parasympathetic nervous system participates in IPR-induced cystatin S gene expression. Bilateral parasympathectomy reduced IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Unilateral parasympathectomy in contrast, had no effect on IPR-induced cystatin S gene expression, suggesting that the presence of an intact parasympathetic innervation in the contralateral side permits the 'normal' IPR-induced expression of the cystatin S gene in the parasympathectomized gland.

Effect of sympathectomy on isoproterenol-induced expression of the cysteine proteinase inhibitor gene, cystatin S, in rat submandibular glands

The autonomic nervous system regulates the secretory function of salivary glands. The volume, rate of secretion and composition of saliva are regulated by both sympathetic (alpha 1-, alpha 2 and beta 1-adrenergic) and parasympathetic (muscarinic and cholinergic) receptor systems. The rat cystatin S gene, a member of family 2 of the cysteine proteinase inhibitor superfamily, has a very defined pattern of expression during the postnatal development of the rat submandibular gland. Its expression is not detected in the fetus or in rats up to three weeks of age. After this time, the amount of cystatin S mRNA increases, reaching a conspicuously high concentration at 28 days, and then it declines to a barely detectable level at 32 days of age; cystatin S mRNA is not detectable in the glands of adult animals. However, the beta-adrenoreceptor agonist isoproterenol (IPR) induces high concentrations of cystatin S mRNA in the submandibular gland in vivo. This paper reports experiments analysing the participation of the sympathetic nervous system in the IPR-induced expression of the cystatin S gene. Sympathetic denervation (unilateral and bilateral) by removing the superior cervical ganglion 14 days before a single injection of IPR reduced the expression of the cystatin S gene. Chemical denervation by reserpine (a drug that depletes neurotransmitters in sympathetic nerve terminals) also reduced IPR-induced expression of the gene. Morphological analyses of sympathectomized and reserpine-treated glands showed that the structure of the gland was similar to that of glands of intact animals and to those not treated with reserpine. The hypertrophic response to IPR was less obvious in the sympathectomized glands, but was similar in reserpine treated animals. Collectively, these data suggest that even in the presence of a functional beta 1-adrenergic receptor pathway, factor(s) from the sympathetic nervous system may be required for IPR-induced expression of the cystatin S gene.

Melanosis of the appendix: prevalence, distribution and review of the pathogenesis of 47 cases

The appendix is reported to be a common site for melanosis, especially at autopsy although to date there have been few studies expanding or qualifying this statement. Based on 47 cases identified from a series of 636 consecutive surgical specimens the prevalence, pattern of distribution, nature of the pigment and current knowledge of the aetiology and pathogenesis of melanosis of the appendix is reviewed and compared with melanosis coli.

Quality improvement in family practice. Program for Pap smears

PROBLEM BEING ADDRESSED

With the increasing emphasis on quality improvement, we need programs for improving office practice.

OBJECTIVE OF PROGRAM

To demonstrate a simple and inexpensive program that resulted in improvement in the quality of Papanicolaou smears in a family practice teaching clinic. The performance measure was the proportion of smears containing endocervical components.

MAIN COMPONENTS OF PROGRAM

The program involved annual feedback on the performance of the physicians in the clinic. Feedback was given to physicians at a regular group meeting; brief discussion of the findings also occurred at that time. There were no other interventions.

CONCLUSIONS

A program involving straightforward feedback and discussion for less than 1 hour contributed to a 7% improvement in the proportion of Pap smears with endocervical components. This "low tech" approach should be tested in other settings and with other procedures and treatments.

Synovial sarcoma of the vulva: a report of two cases

We report two cases of synovial sarcoma arising in the vulva. The patients were 30 and 37 years old and presented with a painless mass that was interpreted clinically as a cyst. The tumors were 2.0 and 1.2 cm in greatest diameter. Histologically, they were composed of epithelial cells forming solid nests and gland-like and papillary structures surrounded by spindle-shaped cells. Immunohistochemically, the epithelial cells stained for cytokeratin and the spindle-shaped cells for vimentin. Ultrastructurally, the epithelial cells had prominent intercellular junctions and narrow microvilli and were separated from the spindle-shaped cells by a basal lamina. The spindle-shaped cells were closely apposed with focal intercellular contacts. One tumor recurred locally 3.5 years after excision, but the patient was alive and well 1 year after a re-excision and radiation therapy. The other patient was alive and well 4 years after an excision. These tumors are the first reported examples of synovial sarcoma arising in the vulva.

Needle size and sample adequacy in ultrasound-guided biopsy of thyroid nodules

OBJECTIVES

To determine the optimal needle size (23-gauge or 27-gauge) for ultrasound-guided fine-needle aspiration biopsy of thyroid nodules and to compare the interoperator yield for this procedure.

PATIENTS AND METHOD

Over an 11-month period, 123 patients underwent biopsy of a thyroid nodule. Three experienced radiologists were assigned at random to sample the nodules. For each nodule, four passes were performed in random order, two with 23-gauge needles and two with 27-gauge needles. If a specific pass yielded no tissue or blood, as determined by visual inspection (i.e., the sample was dry), the procedure was repeated until a satisfactory sample was obtained. After each patient had left the department, the aspirates were reviewed by a cytopathologist (who was not aware of needle size or operator identity) to determine diagnostic adequacy.

RESULTS

Among the 123 nodules, 88 were solid, and 35 were complex cysts. There was no significant difference between the two sizes of needle in the adequacy of the samples obtained (102 nodules were adequately sampled with the 23-gauge needle and 95 with the 27-gauge needle; McNemar chi 2 test, p = 0.1456). However, there were significantly fewer dry passes with the larger needle (2 with the 23-gauge needle and 16 with the 27-gauge needle; chi 2 test, p = 0.0022). Sixteen nodules were inadequately sampled with both needles. Eight of these were less than 1 cm in greatest dimension. Only one solid nodule greater than 1 cm in greatest dimension was inadequately sampled. There was no difference in yield among the three radiologists (chi 2 test, p = 0.5192). No significant complications were encountered.

CONCLUSIONS

Needles of both 23 and 27 gauge can be used to obtain fine-needle aspiration biopsy samples from thyroid nodules. Using both sizes is recommended, because the number of dry passes is lower with the larger needle, but the diagnostic quality of the aspirate may be better with the smaller one. Experienced physicians can perform fine-needle aspiration biopsy with equal proficiency.

MR evaluation of cervical cancer in hysterectomy specimens: correlation of quantitative T2 measurement and histology

Specimens from modified radical hysterectomies performed for invasive carcinoma of the cervix were analyzed with quantitative T2 magnetic resonance (MR) imaging and histologic study to determine to what degree there was a correlation between the findings of the two modalities. The mean T2 of cervical stroma was 48 msec, while the outer zone of the cervix had a mean T2 of 62 msec and the central canal region typically had T2 values of 115 msec +/- 20 (standard deviation). A total of nine cervical cancers were analyzed, and their mean T2 value was 79 msec. Separation between cervical stroma and tumor was good, with stromal T2 values ranging from 30 to 66 msec, while tumor T2s ranged from 60 to 97 msec. Statistical analysis indicated that these data were associated with a sensitivity of 89% and a specificity of 95%, with 95% confidence intervals of [50%, 99.4%] and [74%, 99.7%], respectively, for separating tumor from stroma on the basis of T2 value. Quantitative T2 imaging was found to provide an effective, nonsubjective means of classifying cervical anatomy and neoplastic disease.

The demonstration of a subset of carcinoid tumours of the appendix by in situ hybridization using synthetic probes to proglucagon mRNA

Previous studies using immunohistochemistry have shown variable hormone production by carcinoid tumours of the appendix. In order to confirm the existence of a specific subset of these tumours, in situ hybridization using synthetic oligonucleotide probes to detect pre-proglucagon and pre-proinsulin mRNA was performed in formalin-fixed, paraffin-embedded material from eight tubular carcinoids, 12 insulin carcinoids, and two mucinous carcinoids. The results were correlated with standard silver and mucin stains. All tubular carcinoids but none of the insular or mucinous carcinoids contained proglucagon mRNA. Proinsulin mRNA was not detected in any of the tumours. Tubular carcinoids of the appendix constitute a definable subset of appendiceal carcinoids which have a similar distribution and prognosis to typical insular carcinoids and can be diagnosed on haematoxylin and eosin-stained sections confirmed by routine special stains. The main need for recognition is to avoid confusion with mucinous carcinoids, which have a worse prognosis and may require more aggressive treatment.

Structure, organization and regulation of a rat cysteine proteinase inhibitor-encoding gene

During postnatal development, submandibular glands of rats produce the secretory protein, cystatin S (CysS), which belongs to family 2 of the mammalian cysteine proteinase inhibitor superfamily. While the rat CysS gene is not expressed in the salivary glands of adult rats, it can be induced by isoproterenol (IPR), which acts via beta-adrenergic receptor/adenylate cyclase/cyclic AMP (cAMP) mechanisms. In addition, IPR-induction of CysS mRNA in submandibular glands is more pronounced in females than in males, at both prepuberal and mature ages. These results suggest that sex hormones may participate in the regulation of the rat CysS gene via estrogen-responsive elements (ERE), and IPR induction of this gene supports the hypothesis that cAMP-responsive elements (CRE) may also play a role in regulating CysS gene expression. We have isolated, sequenced and characterized the complete gene. The CysS gene contains three exons interrupted by two intervening sequences, with consensus splice junctions. The transcription start point is 73 nucleotides upstream from the start codon which is surrounded by a typical Kozak sequence. CCAAT and TATA boxes are present in the 5'-flanking region of the CysS gene. This region also contains several possible regulatory elements that resemble those of other eukaryotic genes, i.e., ERE, CRE, and glucocorticoid-responsive elements. The first intron sequence contains other potential CRE highly homologous to those found in the IPR-inducible mouse and hamster proline-rich-protein-encoding genes.

The topographical and age distributions of neuroendocrine cells in the normal human appendix

In order to clarify the histogenesis of appendiceal carcinoid tumours, epithelial (ENC) and subepithelial (SNC) neuroendocrine cells were counted at four sites in 50 normal appendices stained by standard argyrophil and argentaffin techniques. In general, ENC were present in similar number at all sites within the appendix, whereas SNC were more numerous at the tip than at the base. The number of ENC was similar throughout life, apart from an increase in one neonate and some elderly patients, whereas SNC were maximal in young adults. Thus, the topographical and age distributions of SNC, but not those of ENC, parallels the topographical and age incidence of appendiceal carcinoid tumours, suggesting that most appendiceal carcinoid tumours arise from SNC rather than ENC.

Counts of S-100 positive epidermal dendritic cells in Kveim test skin biopsies

S-100 positive epidermal dendritic cells were counted in skin biopsies from 48 Kveim tests and four known foreign-body reactions. Counts in histologically positive Kveim biopsies (mean 11.3 per 200 basal cells) were significantly higher than in either negative biopsies (5.1; P less than 0.001) or foreign-body reactions (4.7; P less than 0.05). A similar difference was found, irrespective of the histological appearances, between biopsies from patients diagnosed clinically as having sarcoidosis (10.5) and those in which another diagnosis had been made (4.1; P less than 0.001). In biopsies from patients with sarcoidosis 70% had a positive Kveim test, 70% had a raised epidermal dendritic cell count and one or the other was positive in 90%. All cases in which both the Kveim test was positive and the dendritic cell count was raised had a final clinical diagnosis of sarcoidosis. Counts of S-100 positive epidermal dendritic cells are useful in differentiating positive reactions to Kveim suspension from non-specific reactions to foreign material and increase the diagnostic confidence of the Kveim test.

The innervation and neuroendocrine cell population of the appendix in total colonic aganglionosis

There is little published information on changes in the appendix in Hirschsprung's disease despite the presence within the mucosa of nerves and neuroendocrine cells together forming a 'neuroendocrine ganglion'. The innervation and neuroendocrine cell population of 11 appendices (two from patients with total colonic aganglionosis, six from patients with short segment Hirschsprung's disease and three normal controls) were examined using H & E, a standard Grimelius silver stain and immunocytochemistry for S-100 protein, neuron-specific enolase, neurofilament and synaptophysin. Compared with both normal and short segment Hirschsprung's disease controls, the total colonic aganglionosis appendices showed decreased numbers of nerve bundles around the muscle layers and within the submucosa, markedly decreased numbers of smaller fibres within the circular muscle and absence of the finer fibres within the lamina propria. There was no change in the overall number of epithelial neuroendocrine cells but subepithelial neuroendocrine cells, normally found in association with mucosal nerve fibres, were totally absent. The concomitant loss of nerve fibres and neuroendocrine cells from the lamina propria in total colonic aganglionosis suggests a different embryological origin for epithelial and sub-epithelial neuroendocrine cells.

In situ adenocarcinoma ex pleomorphic adenoma of the lacrimal gland

We report a unique case of in situ adenocarcinoma ex pleomorphic adenoma of the lacrimal gland. The patient is alive and disease-free 2 1/2 years after complete local excision of the tumour. The current clinicopathologic status of this unusual tumour is discussed in the context of the reported experience to date.

Expression and induction by beta-adrenergic agonists of the cystatin S gene in submandibular glands of developing rats

Repeated administration of the beta-adrenergic agonist isoprenaline (isoproterenol, IPR), which produces hypertrophic/hyperplastic enlargements of rat submandibular and parotid glands, induces synthesis of a secretory protein shown to be a cysteine proteinase inhibitor, rat cystatin S. In the current study, Northern blot and hybridizations in situ were carried out to establish the developmental and beta-adrenergic regulation of the expression of the cystatin S gene. Cystatin S mRNA was not detected in submandibular glands of 20-day-old fetuses, nor in the glands of newborn or 10-day-old rats. However, steady-state levels of cystatin S mRNA increased between 21 and 28 days, reaching a conspicuously high concentration at 28 days; cystatin S mRNA then declined rapidly to a barely detectable level in glands of 32-day-old rats. IPR administration for 4 days induced high levels of cystatin S mRNA in submandibular glands of developing and adult rats. In both prepubertal and mature animals, induction of cystatin S mRNA in submandibular glands was more pronounced in female than in male animals. Hybridizations in situ revealed cystatin S mRNA only in acinar but not in duct cells of the submandibular gland. Developmentally, expression of the cystatin S gene coincided with acinar cell differentiation. These data suggest a complex neural, hormonal and developmental regulation of salivary cystatin genes.

Transrectal fine-needle aspiration and truecut needle biopsy of the prostate: a blinded comparison of accuracy

Transrectal needle aspiration biopsy and core biopsy of the prostate were performed simultaneously on 88 men with prostatic nodules. Cytologic and histologic assessments were made in a blinded, independent fashion, and the results were compared. All patients with positive findings on aspiration also had positive findings on core biopsy, for a positive predictive value for aspiration of 100%. However, five negative and six "insufficient" results obtained by aspiration were positive on core biopsy, for a negative predictive value for aspiration of 88%. This experience support the use of needle aspiration as an initial diagnostic maneuver in the assessment of prostatic nodules.

Beta-adrenergic induction of a cysteine-proteinase-inhibitor mRNA in rat salivary glands

Transcripts encoding the cysteine-proteinase inhibitor rat cystatin S are induced in submandibular and parotid glands by the beta-adrenergic agonist isoproterenol (isoprenaline). High levels of cystatin S mRNA persist in glands of chronically treated animals for 6 days after discontinuation of the catecholamine, indicating a long half-life of the mRNA. Post-transcriptionally the size of the mRNA decreases, owing to a shortening of the poly(A) tail.

Cloning and sequencing of cDNA encoding a rat salivary cysteine proteinase inhibitor inducible by beta-adrenergic agonists

The beta-adrenergic agonist isoproterenol induces a unique secretory protein (LM) in the salivary glands of developing and adult rats. In order to study the regulation of growth and gene expression by catecholamines, we have isolated and sequenced several cDNA clones encoding the LM protein. Each of the LM cDNA clones described identifies, by Northern blot analyses, a single mRNA species of approximately 900 bases in size. The mRNA encoding this secreted protein was not detected in submandibular glands or brains of untreated adult rats. Sequence analyses of the LM cDNA clones revealed a striking similarity to the family 2 of cysteine proteinase inhibitors. Furthermore, when purified LM protein was used to assay for inhibition of cysteine proteinases, the data demonstrated that it is indeed a type of cysteine proteinase inhibitor. This inhibitor, termed rat cystatin S, provides the first example of cysteine proteinase inhibitors that can be induced by beta-adrenergic agonists.

Comparison of immunological detection of 5-hydroxytryptamine by monoclonal antibodies with standard silver stains as an aid to diagnosing carcinoid tumours

Immunoreactivity to a monoclonal antibody against 5-hydroxytryptamine (5HT) was compared with Churukian Schenk argyrophilia and Masson Fontana argentaffin staining as an aid to the diagnosis of 53 carcinoid tumours. Thirty four tumours were argentaffin positive, 50 were argyrophil positive, and 43 contained immunologically detectable 5HT. In general, argentaffin staining and immunological detection of 5HT failed to pick up tumours derived from the foregut of type B or type D morphology. Argentaffin negative tumours usually showed only focal immunoreactivity for 5HT. If immunological detection of 5HT is used alone as a marker for carcinoid tumours problems arise in the differentiation of carcinoid tumours from adenocarcinomas which may also contain 5HT. These results were compared with those culled from other reported techniques used as an aid to the diagnosis of carcinoid tumours.

Carcinoid tumour of the middle ear associated with systemic symptoms

Carcinoid tumour is one of the rarest middle-ear neoplasms. We describe here a case of carcinoid tumour of the middle-ear cleft that presented with aural as well as systemic symptoms. Diagnostic difficulty was encountered using light microscopy, but electron microscopy revealed the neurosecretory granules.

Glycosylation in livers of newborn mice homozygous for a lethal deletion

Endogenous glycoprotein and lipid biosynthesis have been examined in slices of liver and other organs from normal and mutant mice homozygous for a perinatally lethal deletion in chromosome 7. Pronase digests of total glycoproteins, radioactively labeled with glucosamine, followed by Bio-Gel P-6 column chromatography of the resultant glycopeptides, indicate that glycosylation in mutant mouse liver is dramatically reduced compared to that of normal littermates. Pulse-chase experiments suggest that this reduction is not due to a processing event, but rather to reduced biosynthesis. In addition, a quantitative reduction of glycopeptides was observed in mutant livers, when the radioactive peaks from the Bio-Gel P-6 fractionation were pooled and analyzed on a Dowex 50 column, followed by separation on DE-52 columns. Analysis, by affinity chromatography, of radioactively labeled total lipids indicated that homozygous mutant and normal littermate livers have similar quantities of neutral and acidic lipids, including phosphatidylserine, phosphatidylinositol, cerebrosides, and phospholipids. Furthermore, the analysis of other organs indicates that the reduction of glycoprotein synthesis observed in the mutant liver is specific to this organ.

Epidermal growth factor gene expression is regulated differently in mouse kidney and submandibular gland

The concentration of the peptide mitogen epidermal growth factor (EGF) is hormonally and developmentally regulated in the granular convoluted tubule cells of the mouse submandibular gland. Using a labeled EGF nucleic acid probe, we have demonstrated that submandibular gland EGF mRNA concentrations increase during postnatal development of the gland and after the administration of testosterone or thyroid hormone. Recently, it was reported that EGF mRNA is present in kidney as well as a number of other mouse tissues. A comparison of EGF gene regulation in submandibular gland and kidney revealed that kidney EGF mRNA levels also increase during the postnatal period. Opposite sex differences were observed, with submandibular gland levels being about 16-fold higher in the male than in the female and kidney levels being 2- to 4-fold higher in the female than in the male. Renal EGF mRNA concentrations are less responsive to hormones than those in the submandibular gland. Renal EGF was localized immunocytochemically to the cells of distal convoluted tubules.

Trans regulation of the phosphoenolpyruvate carboxykinase (GTP) gene, identified by deletions in chromosome 7 of the mouse

Livers from newborn mice homozygous for either one of the lethal deletions c14CoS or c3H in chromosome 7 have drastically reduced levels of cytosolic phosphoenolpyruvate carboxykinase (GTP) [GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32] activity when compared with normal littermates. The structural gene for the enzyme maps on chromosome 2 and appears intact and not grossly rearranged in deletion homozygotes. These mice also have negligible levels of hepatic mRNA encoding this enzyme. Studies of the transcription rate of the gene showed that it was reduced to 25-50% of normal in hepatic nuclei obtained from mice homozygous for either deletion. We suggest that, in addition to the reduction in the level of transcription, the deletions in chromosome 7 may also cause alterations in messenger stability, processing, or transport from the nucleus.

Effect of advanced age on the induction by androgen or thyroid hormone of epidermal growth factor and epidermal growth factor mRNA in the submandibular glands of C57BL/6 male mice

We have compared the responsiveness of the submandibular glands of mature (12 month old) and senescent (26-28 month old) male C57BL/6 mice to dihydrotestosterone (DHT) or triiodothyronine (T3) in terms of steady state levels of epidermal growth factor (EGF) protein and EGF mRNA. Northern blot analyses did not disclose any differences with age in the apparent sizes of EGF mRNA species. In untreated animals, submandibular glands of 26-28-month-old mice contained approximately 50% less EGF, and 75% less EGF mRNA than those of 12-month-old males. With advanced age, there was a 20% reduction in the absolute volume of the granular convoluted tubule (GCT) compartment, which is the exclusive site of EGF and EGF mRNA in the gland. In general, GCTs of old mice were composed of smaller cells with fewer secretion granules, but there was considerable cell-to-cell variation. In addition, there was greater variation in the intensity of immunocytochemical staining for EGF in senescent GCT cells, which also gave a lower and more variable in situ hybridization signal for EGF mRNA. After hormonal stimulation for 1 week with either tri-iodothyronine (T3) or dihydrotestosterone (DHT), EGF protein concentration in the glands was induced to the same level at both ages. However, EGF mRNA was 50% less abundant in old hormonally stimulated glands, compared to similarly treated young ones. Although many GCT cells in treated glands of senescent males respond to hormonal stimulation by increases in size and in content of secretion granules, there was cell-to-cell variation in responsiveness, especially after treatment with T3. These findings indicate that the decreases seen in the entire gland in EGF and EGF mRNA are caused by a wide-spread deterioration of the GCT cells themselves, which apparently can be reversed in many but not all GCT cells by stimulation with supraphysiologic doses of either T3 or DHT.

Correction of a genetically caused enzyme defect by somatic cell hybridization

Liver cells obtained from newborn mice homozygous for any one of several overlapping deletions in chromosome 7 fail to express a number of liver-specific differentiated traits. Among these is the activity of the membrane-bound liver-specific enzyme glucose-6-phosphatase (Glc-6-Pase; D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9). Previous studies have led to the suggestion that the region of the genome covered by these deletions includes genes that normally regulate the expression of structural genes encoding liver-specific enzymes and proteins mapping elsewhere in the genome. To find out whether the deficiency of Glc-6-Pase may be caused by the deletion of the relevant structural gene, mouse liver cells homozygous for the deletion c14CoS were hybridized with 2S Faza rat hepatoma cells, and the hybrid cell cultures were analyzed for mouse and rat Glc-6-Pase activity. Hybrids showed expression of mouse Glc-6-Pase activity, proving that the structural gene for this enzyme is not included in the deletion c14CoS in chromosome 7. In the hybrid cells the rat hepatoma genome apparently contributes a factor that activates the structural gene of the mouse and corrects its failure of expression, which most likely resulted from the deletion of an essential regulatory or processing gene. By using as a marker glucose-6-phosphate isomerase (Glc-6-PIase; glucosephosphate isomerase, D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9), known to map on chromosome 7, this entire chromosome could be excluded as a possible carrier of the Glc-6-Pase structural gene. In addition, the structural genes for Glc-6-Pase and for tyrosine aminotransferase (TyrATase; L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5), another enzyme deficient in lethal deletion homozygotes, were shown to map on two different chromosomes. Together with our previous studies of TyrATase gene regulation, the present experiments suggest that the region of the mouse genome defined by the deletions includes one or more genes regulating the expression of several structural genes that map on different chromosomes and that encode liver-cell-type specific traits.

Epidermal growth factor and glucagon receptors in mice homozygous for a lethal chromosomal deletion

The binding of epidermal growth factor (EGF) and of glucagon to their receptors has been examined in single-cell suspensions obtained from livers and other organs of newborn mice homozygous for a perinatally lethal deletion that includes the albino (c) locus on chromosome 7. Competition experiments with 125I-labeled and nonradioactive EGF and Scatchard analysis of equilibrium binding data showed that hepatocytes from deletion homozygotes had only approximately equal to 20% of the number of specific EGF receptors present in cells from normal littermates. In contrast, EGF binding to single-cell suspensions from organs other than the liver was normal in deletion homozygotes. Similar results were obtained in competitive displacement experiments with 125I-labeled and nonradioactive glucagon: hepatocytes from deletion mutants showed only approximately equal to 30% of the specific glucagon binding sites found in cells from normal littermates. As in the case of EGF, the decreased binding was due to decreased numbers of glucagon receptors per cell rather than alterations in receptor affinity, and glucagon binding to single-cell suspensions from organs other than the liver was normal in the deletion mutants. The reductions in numbers of EGF and glucagon receptors are liver-cell specific as are the previously described ultrastructural and biochemical abnormalities in these mutants. The significance of cell membrane integrity and hormone-receptor interactions in the control of normal liver cell differentiation is discussed.

Recessive lethal deletion on mouse chromosome 7 affects glucocorticoid receptor binding activities

The hormone binding activity of glucocorticoid receptors is decreased by approximately equal to 75% in the livers of mice homozygous for c14CoS, one of several overlapping radiation-induced deletions on chromosome 7. These deletions have been shown previously to map at and around the albino (c) locus and to act as recessive lethals. They are associated with intractable hypoglycemia, ultrastructural abnormalities in certain liver cell membranes, and deficiencies of specific liver proteins and enzymes that are induced by insulin or glucocorticoids, or both. Scatchard analysis of [3H]dexamethasone binding to receptors in control and mutant liver extracts revealed that the glucocorticoid binding constants were similar; however, the control extracts bound approximately equal to 4 times as much steroid as did mutant extracts. Analysis by DNA-cellulose column chromatography demonstrated that the ability of activated glucocorticoid receptors to form complexes with DNA appears to be unaltered in the mutants; both mutant and control cytosols contain glucocorticoid receptors that elute from DNA-cellulose columns at two different salt concentrations. Sucrose density gradient centrifugation revealed the glucocorticoid receptors in mutant livers to have approximately the same sedimentation coefficient as receptors in control livers. The decrease in glucocorticoid binding activity in mutant liver cell extracts is comparable in degree to that previously reported for insulin binding activity. The gene sequences deleted in the homozygous deletion mutants appear to be instrumental in the regulation rather than the structural determination of both glucocorticoid and insulin receptors.

Genetic control of insulin receptors

Insulin-binding activity was measured in hepatocyte suspensions and liver membrane preparations from newborn mice homozygous for a perinatal-lethal deletion at and around the albino locus in chromosome 7. Cell suspensions and membrane preparations from the mutant mice exhibited only 20-25% of the specific hormone-binding activity observed in comparable preparations from their homozygous normal and heterozygous littermates. The decrease in insulin-binding activity appears to be attributable to a decrease in the number of insulin receptor sites per cell rather than to a change in receptor affinity. Gene sequences deleted at and around the albino locus are therefore instrumental in the regulation of insulin receptor concentration rather than in coding for the insulin receptor itself. The results of the present studies extend the identification of the regulatory functions exerted by the genes around the albino locus of the mouse.

Dinucleotide priming of RNA synthesis

Initiation of RNA synthesis with preformed dinucleotides as primers and either a bacterial or a eukaryotic DNA-dependent RNA polymerase was used to probe sequences on DNA or chromatin that are available for transcription. Using saturating levels of Escherichia coli RNA polymerase or wheat germ RNA polymerase II to transcribe free DNA, a preference was noted for the dinucleotides GpA, GpG, ApG, and UpG for initiation of RNA synthesis. When saturating levels of E. coli RNA polymerase were used to transcribe chromatin, a little preference was noted for UpA and UpC; wheat germ RNA polymerase II, on the other hand, utilized the dinucleotides GpA, ApG, ApA, and UpG more efficiently. Under conditions of limiting amounts of enzyme to transcribe chromatin, wheat germ RNA polymerase preferred to initiate RNA synthesis with the dinucleotide primers GpA, ApA, ApC, and UpG; E. coli RNA polymerase preferred GpA and GpG. These results emphasize both the role of the configuration of the template and the role of the enzyme in sequence selection for initiation of transcription.