One for all or all for one? An integrative review of research on frequent callers

Objective

Telephone health services is an increasing and integral part of health care in several countries. Callers who call repeatedly, in the current study "frequent callers" are present in all kinds of healthcare services, often constitute a considerable proportion of the total amount of calls and are complicated to help. The aim was to provide a comprehensive overview of research on frequent callers at a variety of telephone health services.

Methods

An integrative literature review. Literature was searched for the period 2011-2020 in CINAHL Plus, MEDLINE, APA PsycArticles, APA PsycInfo, and PubMed, and resulted in the inclusion of 20 articles.

Results

Studies on frequent callers (FCs) were found in the context of emergency medical services, telephone helplines, primary healthcare, and specialist medicine clinics. Frequent calling was associated with psychiatric comorbidity, and the reasons for calling were often multifaceted.

Conclusion

The strategies suggested for handling calls involved an individual approach, which could be enabled through multidisciplinary work.

Innovation

The main findings indicate a need for a systematic approach and guidelines to enable optimal help for FCs. Cooperation among healthcare instances seems to contribute to a more individual care for FCs.

Bi-allelic variants in DNA mismatch repair proteins MutS Homolog MSH4 and MSH5 cause infertility in both sexes

STUDY QUESTION

Do bi-allelic variants in the genes encoding the MSH4/MSH5 heterodimer cause male infertility?

SUMMARY ANSWER

We detected biallelic, (likely) pathogenic variants in MSH5 (4 men) and MSH4 (3 men) in six azoospermic men, demonstrating that genetic variants in these genes are a relevant cause of male infertility.

WHAT IS KNOWN ALREADY

MSH4 and MSH5 form a heterodimer, which is required for prophase of meiosis I. One variant in MSH5 and two variants in MSH4 have been described as causal for premature ovarian insufficiency (POI) in a total of five women, resulting in infertility. Recently, pathogenic variants in MSH4 have been reported in infertile men. So far, no pathogenic variants in MSH5 had been described in males.

STUDY DESIGN, SIZE, DURATION

We utilized exome data from 1305 men included in the Male Reproductive Genomics (MERGE) study, including 90 males with meiotic arrest (MeiA). Independently, exome sequencing was performed in a man with MeiA from a large consanguineous family.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Assuming an autosomal-recessive mode of inheritance, we screened the exome data for rare, biallelic coding variants in MSH4 and MSH5. If possible, segregation analysis in the patients' families was performed. The functional consequences of identified loss-of-function (LoF) variants in MSH5 were studied using heterologous expression of the MSH5 protein in HEK293T cells. The point of arrest during meiosis was determined by γH2AX staining.

MAIN RESULTS AND THE ROLE OF CHANCE

We report for the first time (likely) pathogenic, homozygous variants in MSH5 causing infertility in 2 out of 90 men with MeiA and overall in 4 out of 902 azoospermic men. Additionally, we detected biallelic variants in MSH4 in two men with MeiA and in the sister of one proband with POI. γH2AX staining revealed an arrest in early prophase of meiosis I in individuals with pathogenic MSH4 or MSH5 variants. Heterologous in vitro expression of the detected LoF variants in MSH5 showed that the variant p.(Ala620GlnTer9) resulted in MSH5 protein truncation and the variant p.(Ser26GlnfsTer42) resulted in a complete loss of MSH5.

LARGE SCALE DATA

All variants have been submitted to ClinVar (SCV001468891-SCV001468896 and SCV001591030) and can also be accessed in the Male Fertility Gene Atlas (MFGA).

LIMITATIONS, REASONS FOR CAUTION

By selecting for variants in MSH4 and MSH5, we were able to determine the cause of infertility in six men and one woman, leaving most of the examined individuals without a causal diagnosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings have diagnostic value by increasing the number of genes associated with non-obstructive azoospermia with high clinical validity. The analysis of such genes has prognostic consequences for assessing whether men with azoospermia would benefit from a testicular biopsy. We also provide further evidence that MeiA in men and POI in women share the same genetic causes.

STUDY FUNDING/COMPETING INTEREST(S)

This study was carried out within the frame of the German Research Foundation sponsored Clinical Research Unit 'Male Germ Cells: from Genes to Function' (DFG, CRU326), and supported by institutional funding of the Research Institute Amsterdam Reproduction and Development and funds from the LucaBella Foundation. The authors declare no conflict of interest.

Central Diabetes Insipidus Caused by Arginine Vasopressin Gene Mutation: Report of a Novel Mutation and Review of Literature

Familial neurohypophyseal diabetes insipidus (FNDI) is an autosomal dominant hereditary disorder characterized by severe polydipsia and polyuria that usually presents in early childhood. In this study, we describe a new arginine vasopressin (AVP) gene mutation in an ethnic German family with FNDI and provide an overview of disease-associated AVP-gene mutations that are already described in literature. Three members of a German family with neurohypophyseal diabetes insipidus were studied. Isolated DNA from peripheral blood samples was used for mutation analysis by sequencing the whole coding region of AVP-NPII gene. Furthermore, we searched the electronic databases MEDLINE (Pubmed) as well as HGMD, LOVD-ClinVar, db-SNP and genomAD in order to compare our cases to that of other patients with FNDI. Genetic analysis of the patients revealed a novel heterozygote missense mutation in exon 2 of the AVP gene (c.274T>G), which has not yet been described in literature. We identified reports of more than 90 disease-associated mutations in the AVP gene in literature. The novel mutation of the AVP gene seems to cause FNDI in the presented German family. Similar to our newly detected mutation, most mutations causing FNDI are found in exon 2 of the AVP gene coding for neurophysin II. Clinically, it is important to think of FNDI in young children presenting with polydipsia and polyuria.

Action of Newcastle Disease Virus on Human Blood Platelets

Newcastle Disease Virus induces a viscous metamorphosis like process in washed platelets.

This virus liberates from platelets lactic dehydrogenase and pyruvate kinase, depletes their ATP content and impairs their ability to concentrate 5-hydroxy-tryptamine.

Since Newcastle Disease Virus has adenosine triphosphatase activity, a possible role of this viral enzyme in the production of viscous metamorphosis and in inhibition of clot retraction is discussed.

Treatment of platelets by Newcastle Disease Virus or by particulate fraction from normal allantoic fluid causes liberation of a platelet factor 3-like substance.

A novel stop mutation (p.(Gln22*)) of DAX1 (NR0B1) results in late-onset X-linked adrenal hypoplasia congenita

DAX1 (NR0B1) is an orphan nuclear receptor, which plays an important role in development and function of the adrenal glands and gonads. Mutations in DAX1 cause X-linked adrenal hypoplasia congenita (X-linked AHC), which is characterized by adrenal insufficiency (AI) and hypogonadotropic hypogonadism (HHG). Affected boys present with adrenal failure usually in childhood and, later in life, with delayed puberty. However, patients with a late-onset form of X-linked AHC have also been described in the past years. We report a male patient who presented with symptoms of an adrenal crisis at the age of 38 years and was later diagnosed with HHG. Family history was positive with several male relatives diagnosed with AI and compatible with the assumed X-chromosomal inheritance of the trait. Direct sequencing of DAX1 of the patient revealed a hemizygous cytosine-to-thymine substitution at nucleotide 64 in exon 1, which creates a novel nonsense mutation (p.(Gln22*)). In order to compare the clinical presentation of the patient to that of other patients with X-linked AHC, we searched the electronic database MEDLINE (PubMed) and found reports of nine other cases with delayed onset of X-linked AHC. In certain cases, genotype-phenotype correlation could be assumed.

LEARNING POINTS

X-linked AHC is a rare disease characterized by primary AI and hypogonadotropic hypogonadism (HHG). The full-blown clinical picture is seen usually only in males with a typical onset in childhood.Patients with a late-onset form of X-linked AHC have also been described recently. Being aware of this late-onset form might help to reach an early diagnosis and prevent life-threatening adrenal crises.Adult men with primary AI of unknown etiology should be investigated for HHG. Detecting a DAX1 mutation may confirm the clinical diagnosis of late-onset X-linked AHC.In relatives of patients with genetically confirmed X-linked AHC, targeted mutation analysis may help to identify family members at risk and asymptomatic carriers, and discuss conscious family planning.

A patient with novel mutations causing MEN1 and hereditary multiple osteochondroma

We report of a male patient aged 32 years who presented with primary hyperparathyroidism. Three parathyroid glands were resected. At the age of 46 years, nervus facialis irritation was noted, and an MRI scan incidentally revealed a non-functioning pituitary adenoma with affection of the chiasma opticum. The patient underwent transsphenoidal operation resulting in pituitary insufficiency postoperatively. At the same time, primary hyperparathyroidism reoccurred and a parathyroid adenoma located at the thymus was resected. The mother of the patient died early due to multiple tumors. The patient was suspected to have multiple endocrine neoplasia type 1 (MEN1) and genetic analysis was performed. In addition, on clinical examination, multiple exostoses were noticed and an additional genetic analysis was performed. His father was reported to have multiple osteochondromas too. MEN1 was diagnosed in the patient showing a novel heterozygote mutation c.2T>A in exon 2, codon 1 (start codon ATG>AAG;p.Met1?) of the MEN1 gene. In genetic mutational analysis of the EXT1 gene, another not yet known mutation c.1418-2A>C was found in intron 5 of the EXT1 gene (heterozygotic). In conclusion, we report novel mutations of the EXT1 and the MEN1 genes causing hereditary multiple osteochondromas and MEN1 in one patient.

LEARNING POINTS

It is important to ask for the patient's family history in detail.Patients with MEN1 are characterized by the occurrence of tumors in multiple endocrine tissues and nonendocrine tissues, most frequently parathyroid (95%), enteropancreatic neuroendocrine (50%), and anterior pituitary (40%) tissues.Familiar MEN1 has a high degree of penetrance (80-95%) by the age over 50; however, combinations of the tumors may be different in members of the same family.Patients with EXT1 gene mutations should be monitored for possible transformation of bone lesions into osteochondrosarcoma.

Next generation sequencing as a useful tool in the diagnostics of mosaicism in Alport syndrome

Alport syndrome (ATS) is a progressive hereditary nephropathy characterized by hematuria and/or proteinuria with structural defects of the glomerular basement membrane. It can be associated with extrarenal manifestations (high-tone sensorineural hearing loss and ocular abnormalities). Somatic mutations in COL4A5 (X-linked), COL4A3 and COL4A4 genes (both autosomal recessive and autosomal dominant) cause Alport syndrome. Somatic mosaicism in Alport patients is very rare. The reason for this may be due to the difficulty of detection. We report the case of a boy and his mother who presented with Alport syndrome. Mutational analysis showed the novel hemizygote pathogenic mutation c.2396-1G>A (IVS29-1G>A) at the splice acceptor site of the intron 29 exon 30 boundary of the COL4A5 gene in the boy. The mutation in the mother would not have been detected by Sanger sequencing without the knowledge of the mutational analysis result of her son. Further investigation of the mother using next generation sequencing showed somatic mosaicism and implied potential germ cell mosaicism. The mutation in the mother has most likely occurred during early embryogenesis. Analysis of tissue of different embryonic origin in the mother confirmed mosaicism in both mesoderm and ectoderm. Low grade mosaicism is very difficult to detect by Sanger sequencing. Next generation sequencing is increasingly used in the diagnostics and might improve the detection of mosaicism. In the case of definite clinical symptoms of ATS and missing detection of a mutation by Sanger sequencing, mutational analysis should be performed by next generation sequencing.

A new mutation in the menin gene causes the multiple endocrine neoplasia type 1 syndrome with adrenocortical carcinoma

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant tumor syndrome that may be caused by mutations in the MEN1 gene on 11q13. Loss of function of the tumor suppressor gene MEN1 leads to synchronous or metachronous appearance of neuroendocrine tumors arising from neuroendocrine cells of the parathyroid and pituitary glands, the duodenum and pancreatic islets, and other endocrine organs such as the adrenal cortex. We here present a patient with MEN1 who developed hyperparathyroidism, multiple well differentiated functionally inactive neuroendocrine tumors of the pancreas and an adrenal carcinoma. We describe a new mutation at codon 443 in the coding region of exon 9 in the MEN1 gene, where a cytosine residue was exchanged for adenosine (TCC > TAC) and, consequently, serine for tyrosine (p.Ser443Tyr; c.1328C > A). [corrected] Also, we provide clinical data that may add to the genotype-phenotype discussion. We conclude that the novel mutation in the MEN1 gene described herein was clinically relevant.

Cushing's disease in a patient with steroid 21-hydroxylase deficiency

Cushing's disease rarely appears as a consequence of hereditary disease. However, familial diseases with diminished glucocorticoid feedback are associated with secondary hypercorticotropinism and have been shown to give rise to pituitary adenomas. We here describe the rare case of a 30-year old female patient with congenital adrenal hyperplasia who also showed clinical signs and a typical history of hypercortisolism that was specified as Cushing's disease. After removal of a pituitary microadenoma, serum-cortisol levels fell below normal and the symptoms improved. However, after four years the menstrual cycle was irregular again and ACTH levels were in the upper range of normal. A corticotropin challenge showed a minor cortisol response but a marked increase in 17-hydroxyprogesterone serum concentrations. Genetic analysis revealed a homozygous mutation in exon 7 of the CYP21A2 gene (CTG>TTG, p.V281L). We conclude that a marked ACTH drive was able to override insufficient 21-hydroxylation and even to cause hypercortisolism. Although we describe a rare case, the impairment of the glucocorticoid feedback system in the context of congenital adrenal hyperplasia and other diseases may contribute to the development of secondary hypercorticotropinism as well as corticotropin producing adenomas.

Functional consequences of seven novel mutations in the CYP11B1 gene: four mutations associated with nonclassic and three mutations causing classic 11{beta}-hydroxylase deficiency

CONTEXT

Steroid 11beta-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia (CAH). Cases of nonclassic 11OHD are rare compared with the incidence of nonclassic 21-hydroxylase deficiency.

OBJECTIVE

The aim of the study was to analyze the functional consequences of seven novel CYP11B1 mutations (p.M88I, p.W116G, p.P159L, p.A165D, p.K254_A259del, p.R366C, p.T401A) found in three patients with classic 11OHD, two patients with nonclassic 11OHD, and three heterozygous carriers for CYP11B1 mutations.

METHODS

We conducted functional studies employing a COS7 cell in vitro expression system comparing wild-type (WT) and mutant CYP11B1 activity. Mutants were examined in a computational three-dimensional model of the CYP11B1 protein.

RESULTS

All mutations (p.W116G, p.A165D, p.K254_A259del) found in patients with classic 11OHD have absent or very little 11beta-hydroxylase activity relative to WT. The mutations detected in patients with nonclassic 11OHD showed partial functional impairment, with one patient being homozygous (p.P159L; 25% of WT) and the other patient compound heterozygous for a novel mild p.M88I (40% of WT) and the known severe p.R383Q mutation. The two mutations detected in heterozygous carriers (p.R366C, p.T401A) also reduced CYP11B1 activity by 23 to 37%, respectively.

CONCLUSION

Functional analysis results allow for the classification of novel CYP11B1 mutations as causative for classic and nonclassic 11OHD, respectively. Four partially inactivating mutations are predicted to result in nonclassic 11OHD. These findings double the number of mild CYP11B1 mutations previously described as associated with mild 11OHD. Our data are important to predict phenotypic expression and provide important information for clinical and genetic counseling in 11OHD.

Analysis of rare APC variants at the mRNA level: six pathogenic mutations and literature review

In monogenic disorders, the functional evaluation of rare, unclassified variants helps to assess their pathogenic relevance and can improve differential diagnosis and predictive testing. We characterized six rare APC variants in patients with familial adenomatous polyposis at the mRNA level. APC variants c.531 + 5G>C and c.532-8G>A in intron 4, c.1409-2_1409delAGG in intron 10, c.1548G>A in exon 11, and a large duplication of exons 10 and 11 result in a premature stop codon attributable to aberrant transcripts whereas the variant c.1742A>G leads to the in-frame deletion of exon 13 and results in the removal of a functional motif. Mutation c.1548G>A was detected in the index patient but not in his affected father, suggesting mutational mosaicism. A literature review shows that most of the rare APC variants detected by routine diagnostics and further analyzed at the transcript level were evaluated as pathogenic. The majority of rare APC variants, particularly those located close to exon-intron boundaries, could be classified as pathogenic because of aberrant splicing. Our study shows that the characterization of rare variants at the mRNA level is crucial for the evaluation of pathogenicity and underlying mutational mechanisms, and could lead to better treatment modalities.

Czech dysplasia: report of a large family and further delineation of the phenotype

Czech dysplasia (OMIM 609162) is a recently delineated COL2A1 disorder characterized by early-onset progressive pseudorheumatoid arthritis, platyspondyly, short third and fourth metatarsals, normal height, and the absence of ophthalmological problems or cleft palate. Czech dysplasia is caused by a specific missense mutation (R275C, c.823C > T) in the triple helical domain of the COL2A1 gene. We report on a large family with 11 patients with typical Czech dysplasia and sensorineural hearing loss. Hearing loss has hitherto not been considered as a major manifestation of Czech dysplasia. Mutation analysis documented the COL2A1 c.823C > T (R275C) mutation in all affected individuals. Thus, Czech dysplasia is possibly caused exclusively by the R275C mutation, which is a unique situation among the COL2A1 disorders. The family provides further evidence for the remarkably uniform manifestation of the clinical and radiological abnormalities and adds hearing loss to the list of major anomalies of Czech dysplasia.

[Multiple endocrine neoplasia 2a: late manifestation of a newly-discovered mutation]

HISTORY

A 55-year-old patient presented with a painless right-sided cervical swelling, which had been present for four months and seemed to get larger. The patient denied dyspnea, dysphagia, "a lump in the throat" or thyroid disease. Two of his paternal aunts had thyroid carcinoma and an adrenal tumor.

INVESTIGATIONS

Ultrasonography revealed an enlarged lymphoid nodule and a large lesion in the right thyroid lobe, the latter with deficient technetium uptake on scintigraphy.

THERAPY AND COURSE

A total thyroidectomy with bilateral centrocervical and lateral neck dissection was performed. Histology revealed a bilateral medullary thyroid carcinoma [MTC: pT3, pN1b (9/34), pM0 (UICC 2002)] and the genetic screening showed a double mutation in codon 611 (TGC>TAT; p.Cys611Tyr; C611Y), and exon 10 of the RET proto-oncogene, which has not been described before. Pheochromocytoma and hyperparathyroidism were excluded. Genetic screening of all close family members was initiated and showed that four of them were gene carriers. Three of them have been operated and a MTC found.

CONCLUSION

The described newly discovered mutation is associated with MTC and pheochromocytoma. This case underlines the need of genetic screening in all patients who present with a MTC only, no matter what the person's age of manifestation, even in the absence of any other MEN-related disease.

Induction of mRNA for tumor necrosis factor-alpha and interleukin-1 beta in mice brain, spleen and liver in an animal model of Shigella-related seizures

BACKGROUND

The pathogenesis of neurological symptoms, the most common extraintestinal complication of childhood shigellosis, is unclear. To elucidate the mechanisms involved, we developed an animal model and demonstrated that TNF alpha and IL-1 beta play a role.

OBJECTIVES

To determine whether TNF alpha and IL-1 beta genes are expressed in the brain following peripheral administration of Shigella dysenteriae 60R.

METHODS

Expression of mRNA for TNF alpha and IL-1 beta was examined in the brain structures (hypothalamus and hippocampus) and peripheral organs by reverse transcriptase polymerase chain reaction, at different time points after intraperitoneal injection of S. dysenteriae sonicate.

RESULTS

In our animal model of Shigella-related seizures, TNF alpha and IL-1 beta mRNA were induced in the brain, spleen and liver already 1 hour after injection of S. dysenteriae sonicate. The expression of TNF alpha and IL-1 beta mRNA in spleen, hippocampus and hypothalamus decreased after 6 h and increased again at 18 h post-injection.

CONCLUSIONS

Local production of TNF alpha and IL-1 beta in the brain may be involved in the enhanced seizure response of mice after administration of S. dysenteriae. It is possible that intracerebral production of TNF alpha and IL-1 beta plays a role in neurological disturbances of human shigellosis.

Role of nitric oxide in the enhancement of pentylenetetrazole-induced seizures caused by Shigella dysenteriae

Convulsions and encephalopathy are frequent complications of childhood shigellosis. We studied the role of nitric oxide (NO) in Shigella-related seizures in an animal model. Pretreatment of mice with Shigella dysenteriae 60R sonicate elevated serum NO levels and enhanced the convulsive response to pentylenetetrazole (PTZ), as indicated by a higher mean convulsion score and a higher number of mice responding with seizures. Treatment of the mice with S-methylisothiourea sulfate (SMT), a potent inhibitor of inducible NO synthase (NOS), prevented the elevation of serum NO levels and concomitantly reduced the enhanced response to PTZ. The mean convulsion scores were 0.7, 0.7, 1.3, and 0.8 for mice treated with saline, saline and SMT, S. dysenteriae 60R sonicate, and S. dysenteriae 60R sonicate with SMT, respectively (P = 0.001 for 60R sonicate versus saline and P = 0.013 for 60R sonicate versus 60R sonicate with SMT). The corresponding seizure rates were 40, 44, 75, and 47% for saline, saline with SMT, S. dysenteriae 60R sonicate, and S. dysenteriae 60R sonicate with SMT, respectively (P = 0.0004 for 60R sonicate versus saline and P = 0.005 for 60R sonicate versus 60R sonicate with SMT). In contrast, injection of N-nitro-L-arginine, a selective inhibitor of constitutive NOS, neither abolished the elevation of serum NO nor attenuated the enhancement of seizures. These findings indicate that NO, induced by S. dysenteriae 60R sonicate, is involved in enhancing the susceptibility to seizures caused by S. dysenteriae.

Involvement of tumor necrosis factor alpha and interleukin-1beta in enhancement of pentylenetetrazole-induced seizures caused by Shigella dysenteriae

Neurologic manifestations, mainly convulsions, are the most frequent extraintestinal complications of shigellosis. We used an animal model to study the roles of tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1beta) in Shigella-related seizures. Administration of Shigella dysenteriae 60R sonicate enhanced the sensitivity of mice to the proconvulsant pentylenetetrazole (PTZ) within 7 h. This was indicated by a significantly higher mean convulsion score and an increased number of mice responding with clonic-tonic seizures in the Shigella-pretreated group. Preinjection of mice with anti-murine TNF-alpha (anti-mTNF-alpha) or anti-murine IL-1beta (anti-mIL-1beta) 30 min prior to administration of Shigella sonicate abolished their enhanced response to PTZ at 7 h. Mean convulsion scores were reduced by anti-mTNF-alpha from 1.2 to 0.8 (P = 0.017) and by anti-mIL-1beta from 1.3 to 0.7 (P = 0.008). Preinjection of anti-mTNF-alpha also reduced the percentage of mice responding with clonic-tonic seizures, from 48 to 29% (P = 0.002), and preinjection of anti-mIL-1beta reduced it from 53 to 21% (P = 0. 012). Neutralization of TNF-alpha or IL-1beta did not protect the mice from death due to S. dysenteriae 60R. These findings indicate that TNF-alpha and IL-1beta play a role in the very early sensitization of the central nervous system to convulsive activity after S. dysenteriae administration. Similar mechanisms may trigger neurologic disturbances in other infectious diseases.

Induction of tumor necrosis factor and nitric oxide by Shigella strains isolated from patients with or without neurologic manifestations

The pathogenesis of the Shigella-associated neurological symptoms is unclear. We examined the potential role of host factors. Sonicates of Shigella strains isolated from children with and without neurologic disturbances were compared regarding their ability to induce tumor necrosis factor (TNF) and nitric oxide (NO) in vitro, in mouse macrophage J744 cell line. The mean concentrations of TNF (14.6 vs. 4.4 ng/ml) and NO (7.4 vs. 3.7 microM) induced were higher in response to strains isolated from children with neurologic complications; the differences were not statistically significant. TNF was also measured in plasma of children with shigellosis, and was found to be elevated in all patients. The mean concentration of TNF in plasma of children with neurologic manifestations was higher than that of children with no neurologic symptoms (450 vs. 138 pg/ml, P <0.05). It is concluded that TNF and NO may play a role in the development of neurologic manifestations of shigellosis.

Induction of nitric oxide production in mouse macrophages by Shiga toxin

Host mediators play an important role in the pathogenesis of shigellosis and Shiga toxin toxicity. Nitric oxide (NO) production in mouse peritoneal macrophages and in the macrophage J744 cell line in response to purified Shiga toxin and lipopolysaccharide (LPS) from Shigella flexneri were studied. Shiga toxin induced NO production in a dose-dependent manner up to 800 ng/ml. Detectable levels of NO were present as early as 4 h after induction and continued to increase during 72 h; Shiga toxin induced greater NO production with time than did LPS. Pre-treatment of Shiga toxin (400 ng/ml) or LPS (10 ng/ml) with polymyxin B, which inactivates LPS, reduced their ability to induce NO by 28% and 96%, respectively. Induction in the presence of anti-TNF alpha antibodies did not reduce the amount of NO in the supernate. These studies showed that Shiga toxin induces NO production in murine macrophages.

The immunosuppressive human placental ferritin subunit p43 is produced by activated CD4+ lymphocytes

Human placental ferritin is an immunosuppressive protein composed of a 43-kDa subunit (p43) and ferritin light chains. Its physiological action seems to be downregulation of the immune response of the mother against her embryo. Elevated levels of p43 in serum are associated with pregnancy, lymphomas, breast cancer, and AIDS. Although it is known that p43 is produced by activated T lymphocytes, the specific T-lymphocyte subset involved is unknown. p43 is measured by enzyme-linked immunosorbent assays with CM-H-9 monoclonal antibody specific for p43. We studied the de novo biosynthesis of p43 by isolated activated CD4+ and CD8+ T lymphocytes in a normal donor and in a patient with elevated levels of p43 in serum. The results indicated that p43 was synthesized by activated CD4+ lymphocytes from the normal donor (0.45% of the total de novo proteins) but that its biosynthesis by CD8+ lymphocytes was below the level of detection. The activated CD4+ lymphocytes from the patient with elevated levels of p43 in serum overproduced p43 (3.8% of the nascent proteins). Since it was shown that a subset of CD8+ lymphocytes has receptors for p43, the latter may be considered an immunoregulatory cytokine produced mainly by activated CD4+ lymphocytes.

The effect of shiga toxin and sonicates of Shigella isolates from children with neurologic manifestation on neuroblastoma cell lines

Although neurologic manifestations are frequent during childhood shigellosis, their pathogenesis is unclear and controversial. Shiga toxin and other cytotoxins are often implicated, but their effect on neuronal cells has not been determined. We examined the effect of purified Shiga toxin and sonicates of Shigella isolates from children with neurologic symptoms on well-characterized human neuroblastoma cells in vitro. Quantitative determinations showed high cytotoxicity of Shiga toxin on HeLa cells (1.2 x 10(6) CD50/mg purified toxin), but no effect on LA-N-1, LA-N-5 and IMR neuroblastoma cell lines. Pretreatment with tumor necrosis factor, which increases expression of the Shiga toxin receptor, globotriosyl ceramide, in endothelial cells and enhanced Shiga toxin cytotoxicity, did not affect the susceptibility of neuroblastoma cells to the toxin. Low dilutions (up to 1:16-1:64) of sonicates of Shigella isolates from children with neurologic symptoms caused agglutination of neuroblastoma cells, but no cell killing was observed morphologically. This study shows that Shiga toxin does not exhibit cytotoxic activity on the human neuroblastoma cell lines examined, neither do sonicates of relevant Shigella strains. The mechanism and significance of the agglutination activity on neuroblastoma cells should be further studied.

Mosaicism in 45,X Turner syndrome: does survival in early pregnancy depend on the presence of two sex chromosomes?

Cytogenetic and molecular genetic findings in 91 patients with Turner syndrome are reported. In 87 patients, chromosome studies were carried out both in lymphocyte and fibroblast cultures. Mosaicism was demonstrated in 58 of these patients (66.7%), whereas only 18 (20.7%) were apparent non-mosaic 45,X, and 11 patients (12.6%) showed non-mosaic structural aberrations of the X chromosome. Among the mosaic cases 16 (18.4% of all patients) displayed a second cell line containing small marker chromosomes. The association of Y-specific chromosomal material with the presence of marker chromosomes was demonstrated in 6 out of 7 mixoploid fibroblast cell lines by polymerase chain reaction amplification and by Southern-blot analysis. The observation of ring formation and morphological variability in vivo and in vitro, and the continuous reduction in the percentage of cells containing marker chromosomes in longterm cultivation experiments indicated an increased instability of marker chromosomes. The findings suggest that in vivo selection of structurally altered sex chromosomes exists. Thus, the observation of apparent non-mosaic 45,X chromosomal complements in liveborn individuals with Turner syndrome does not contradict the hypothesis that some degree of mosaicism is necessary for survival in early pregnancy.

Dimethyl sulfoxide-induced differentiation does not alter tumorigenicity of neuroblastoma cells

It has been shown that agents that are known to be scavengers of hydroxyl radicals may induce differentiation and inhibit growth of murine neuroblastoma cells in tissue culture. The present study tests dimethyl sulfoxide as a differentiation agent of the human neuroblastoma cell lines LA-N-1 and murine neuroblastoma NIE-115. Results indicate that DMSO induces morphologic and biochemical differentiation of neuroblastoma cells coupled to growth inhibition and inhibition of colony formation in semi liquid tissue culture systems. DMSO treatment in vitro had no effect on tumorigenicity of NIE-115 cells. In vivo DMSO treatment of athymic nude mice with transplanted LA-N-1 human neuroblastoma tumors has not affected tumor size or animal survival. No diminishing effect of natural killer cell activity could be attributed to DMSO treatment.

Rabbit skeletal muscle F-actin can be stable at low ionic strength, provided trace amounts of Ca2+ are absent

Addition of low concentrations (0.2--2.0 mM) of EGTA to rabbit skeletal muscle G-actin in the presence of ATP caused increase in viscosity. The effect is probably due to chelation of Ca2+. EGTA-polymerized actin was sedimented in the ultracentrifuge as a pellet which could be depolymerized in the presence of Ca2+ and then repolymerized. Electron microscopy indicated that formation of filamentous actin which appears to be somewhat more flexible than F-actin obtained by polymerization with KCl. The EGTA-polymerized actin was dissociated by DNAase I faster than KCl-polymerized actin. F-Actin can thus be stable also in very low ionic strength media if Ca2+ is removed whereas for G-actin to be the only form of the protein in such media, micromolar concentrations of Ca2+ must be present.