Perinatal germ cell development and differentiation in the male marmoset (Callithrix jacchus): similarities with the human and differences from the rat.

STUDY QUESTION: Is perinatal germ cell (GC) differentiation in the marmoset similar to that in the human? SUMMARY ANSWER: In a process comparable with the human, marmoset GC differentiate rapidly after birth, losing OCT4 expression after 5-7 weeks of age during mini-puberty. WHAT IS KNOWN ALREADY: Most of our understanding about perinatal GC development derives from rodents, in which all gonocytes (undifferentiated GC) co-ordinately lose expression of the pluripotency factor OCT4 and stop proliferating in late gestation. Then after birth these differentiated GC migrate to the basal lamina and resume proliferation prior to the onset of spermatogenesis. In humans, fetal GC differentiation occurs gradually and asynchronously and OCT4(+) GC persist into perinatal life. Failure to switch off OCT4 in GC perinatally can lead to development of carcinoma in situ (CIS), the precursor of testicular germ cell cancer (TGCC), for which there is no animal model. Marmosets show similarities to the human, but systematic evaluation of perinatal GC development in this species is lacking. Similarity, especially for loss of OCT4 expression, would support use of the marmoset as a model for the human and for studying CIS origins. STUDY DESIGN, SIZE AND DURATION: Testis tissues were obtained from marmosets (n = 4-10 per age) at 12-17 weeks' gestation and post-natal weeks 0.5, 2.5, 5-7, 14 and 22 weeks, humans at 15-18 weeks' gestation (n = 5) and 4-5 weeks of age (n = 4) and rats at embryonic day 21.5 (e21.5) (n = 3) and post-natal days 4, 6 and 8 (n = 4 each). PARTICIPANTS/MATERIALS, SETTING AND METHODS: Testis sections from fetal and post-natal marmosets, humans and rats were collected and immunostained for OCT4 and VASA to identify undifferentiated and differentiated GC, respectively, and for Ki67, to identify proliferating GC. Stereological quantification of GC numbers, differentiation (% OCT4(+) GC) and proliferation were performed in perinatal marmosets and humans. Quantification of GC position within seminiferous cords was performed in marmosets, humans and rats. MAIN RESULTS AND ROLE OF CHANCE: The total GC number increased 17-fold from birth to 22 post-natal weeks in marmosets; OCT4(+) and VASA(+) GC proliferated equally in late gestation and early post-natal life. The percentage of OCT4(+) GC fell from 54% in late fetal life to <0.5% at 2.5 weeks of age and none were detected after 5-7 weeks in marmosets. In humans, the percentage of OCT4(+) GC also declined markedly during the equivalent period. In marmosets, GC had begun migrating to the base of seminiferous cords at ∼22 weeks of age, after the loss of GC OCT4 expression. LIMITATIONS, REASONS FOR CAUTION: There is considerable individual variation between marmosets. Although GC development in marmosets and humans was similar, there are differences with respect to proliferation during fetal life. The number of human samples was limited. WIDER IMPLICATIONS OF THE FINDINGS: The similarities in testicular GC differentiation between marmosets and humans during the perinatal period, and their differences from rodents, suggest that the marmoset may be a useful model for studying the origins of CIS, with relevance for the study of TGCC. STUDY FUNDING/COMPETING INTERESTS: This work was supported by Grant G33253 from the Medical Research Council, UK. No external funding was sought and there are no competing interests.

Maternal communication style, problem-solving and dietary adherence in young children with type 1 diabetes.

The incidence of type 1 diabetes (T1D) in young children is increasing markedly however young children have been overlooked in paediatric adherence research despite the unique challenges their care presents. We investigated the relation between maternal communication style and adherence to the dietary regimen in 40 children with T1D, aged 2-8 years, and their mothers. Mothers completed measures of children's sugar consumption, parent-child communication quality, and child psychological functioning. Mothers and children engaged in a videotaped problem-solving task related to the dietary regimen, with maternal utterances analysed for behavioural control style (e.g., commands versus suggestions) and cognitive complexity (e.g., provision of labels versus questions). Maternal communications which engaged children, behaviourally and cognitively, in the task were associated with better adherence, medical, communication quality, and child adjustment outcomes. We conclude that adherence and health (medical and psychological) are optimized when young children are given opportunities to participate in their care.

Xenografting of human fetal testis tissue: a new approach to study fetal testis development and germ cell differentiation.

BACKGROUND: Abnormal fetal testis development can result in disorders of sex development (DSDs) and predispose to later testicular dysgenesis syndrome (TDS) disorders such as testicular germ cell tumours. Studies of human fetal testis development are hampered by the lack of appropriate model, and intervention systems. We hypothesized that human fetal testis xenografts can recapitulate normal development. METHODS: Human fetal testes (at 9 weeks, n = 4 and 14-18 weeks gestation, n = 6) were xenografted into male nude mice for 6 weeks, with or without hCG treatment of the host, and evaluated for normal cellular development and function using immunohistochemistry, triple immunofluorescence and testosterone assay. The differentiation and proliferation status of germ cells within xenografts was quantified and compared with age-matched controls. RESULTS: Xenografts showed >75% survival with normal morphology. In the first-trimester xenografts seminiferous cord formation was initiated and in first- and second-trimester grafts normal functional development of Sertoli, Leydig and peritubular myoid cells was demonstrated using cell-specific protein markers. Grafts produced testosterone when hosts were treated with hCG (P = 0.004 versus control). Proliferation of germ cells and differentiation from gonocytes (OCT4(+)) into pre-spermatogonia (VASA(+)) occurred in grafts and quantification showed this progressed comparably with age-matched ungrafted controls. CONCLUSIONS: Human fetal testis tissue xenografts demonstrate normal structure, function and development after xenografting, including normal germ cell differentiation. This provides an in vivo system to study normal human fetal testis development and its susceptibility to disruption by exogenous factors (e.g. environmental chemicals). This should provide mechanistic insight into the fetal origins of DSDs and TDS disorders.

Effect of fetal or neonatal exposure to monobutyl phthalate (MBP) on testicular development and function in the marmoset.

BACKGROUND: Fetal exposure of male rats to some phthalates induces reproductive abnormalities, raising concerns for similar effects in humans. In order to address this in a more appropriate animal model, the aim of the present studies was to investigate the effect of fetal/neonatal exposure to monobutyl phthalate (MBP) in a non-human primate, the marmoset. In particular, to determine if exposure resulted in effects at birth, or in adulthood, similar to those in male rats, and whether there was evidence for induction of carcinoma-in-situ (CIS) or testicular germ cell tumours (TGCT). METHODS: Pregnant female marmosets were dosed from approximately 7-15 weeks gestation with 500 mg/kg/day MBP and male offspring studied at birth (1-5 days; n = 6) or in adulthood (n = 5). In another study, newborn males (n = 5 co-twins) were dosed with 500 mg/kg/day MBP for 14 days, commencing at approximately 4 days of age. RESULTS: Fetal exposure of marmosets to MBP did not affect gross testicular morphology, reproductive tract development or testosterone levels at birth, nor were germ cell number and proliferation, Sertoli cell number or germ:Sertoli cell ratio affected. In two of six MBP-exposed animals, unusual clusters of undifferentiated germ cells were found, but their significance is unclear. Neonatal MBP treatment did not affect germ cell numbers or differentiation. Fetal exposure to MBP did not affect testis size/morphology, germ cell numbers or fertility in adulthood. There was no evidence for CIS or TGCT. CONCLUSIONS: Fetal exposure of marmosets to MBP does not measurably affect testis development/function or cause testicular dysgenesis, and no effects emerge by adulthood. Some effects on germ cell development were found, but these were inconsistent and of uncertain significance.

Audit of microalbumin excretion in children with type I diabetes.

OBJECTIVE: To investigate prevalence, persistence and clinical correlates of increased microalbumin excretion in random urine samples collected in a paediatric diabetes clinic. METHOD: Random urine samples were collected annually in patients >10 years attending the diabetes clinic in the Royal Hospital for Sick Children, Edinburgh. Albumin excretion is expressed as albumin:creatinine ratio (ACR) and classified as normal (10 mg/mmol), or macroalbuminuria (>47 mg/mmol in females, >35 mg/mmol in males). We analyzed retrospectively results on 421 urine samples collected from 217 patients (109 males), of a median age of 12.3 years (94% 10-16 years) over 3 years. For each sample, the corresponding mean HbA1c over the previous year was calculated. RESULTS: Prevalence of micro- and macro-albuminuria in individual samples was 1% and 0.5% respectively. ACR was equivocal in 10.1% and 4.7% in samples from females and males respectively (p=0.03). HbA1c showed borderline significant differences across ACR groups (p=0.06). Equivocal ACR excretion was associated with slightly higher mean HbA1c (9.5±1.3%) compared to normal albuminuria (9.0±1.1%, p3.5 mg/mmol. The 14-16 years age group patients were most likely to have ACR >3.5 mg/mmol (p=0.05). CONCLUSIONS: Female sex and increasing age, but not HbA1c, were independently associated with increased ACR. A robust mechanism for collection of repeat early morning urine samples from patients with increased ACR in random urine samples, and follow-up of those patients who have persistently high microalbumin excretion are important. It is also important to confirm the usefulness of ACR measurements in random urine samples as a marker of incipent nephropathy.

Predictors of treatment adherence in young children with type 1 diabetes.

AIM: This paper reports a study to investigate whether diabetes-specific, demographic and psychosocial variables predict adherence in young children with type 1 diabetes. BACKGROUND: Paediatric diabetes rates are increasing worldwide; however, young children are neglected in treatment adherence research, despite the importance of adherence for health. Greater understanding of adherence in this group could enhance nurses' ability to provide care tailored to families' needs. METHOD: A cross-sectional study was carried out between 2001 and 2003 with 65 children aged 2-8 years and their mothers in Britain. Mothers were interviewed about children's diabetes care, nutritional analyses were conducted and mothers completed assessments of diabetes knowledge, parenting stress, family functioning and child psychological adjustment. Demographic and medical information was collected from patient records. FINDINGS: Consistent with older populations, blood glucose monitoring and dietary regimens showed greater adherence variability than injection frequency and injection time consistency. Better maternal diabetes knowledge correlated with less injection time variability, more frequent blood glucose monitoring, lower percentage energy intake from extrinsic sugars, lower glycosylated haemoglobin levels and fewer relationship difficulties. Longer diabetes duration, greater injection time variability and higher percentage energy intake from extrinsic sugars predicted less frequent blood glucose monitoring. More relationship difficulties and less frequent blood glucose monitoring predicted higher percentage energy intake from extrinsic sugars. CONCLUSIONS: Nurses can facilitate treatment adherence through provision of educational, practical and socio-emotional support. Nursing interventions should target blood glucose monitoring and dietary regimens in particular, and nurses should be sensitive to the various caretaking challenges presented to parents by different components of the diabetes regimen.

The role of somatropin therapy in children with Noonan syndrome.

Patients with Noonan syndrome, which is thought to have an incidence of 1 : 1,000 to 1 : 2,500 live births, have variable hypogonadism together with features such as pulmonary valvular stenosis, dysmorphism, deafness, visual problems, cryptorchidism, clotting disorders, and short stature. Noonan syndrome is now known to be associated with mutations in the PTPN11 gene encoding the protein tyrosine phosphatase SHP-2 on chromosome 12 (12q24.1). This discovery will facilitate both knowledge of the true incidence and phenotypic diversity. There are poor genotype-phenotype correlations in Noonan syndrome, and the currently defined gene abnormalities only account for a minority of those identified on a clinical basis. Puberty in patients with Noonan syndrome generally occurs spontaneously but is typically delayed. Mean adult height is 162.5cm (men) and 153cm (women), although standards are based on relatively small samples of largely cross-sectional data and are subject to ascertainment bias. Available evidence suggests that there may be disturbance of the growth hormone/insulin-like growth factor axis in Noonan syndrome and that somatropin (growth hormone therapy) dose-dependently improves vertical growth in the short to medium-term. Final height data from a number of European studies will be available later in 2003. Noonan syndrome patients with echocardiographic features of hypertrophic cardiomyopathy may be at particular risk from somatropin therapy because of its known effects on cardiac muscle mass; these patients have generally been excluded from trials of somatropin. Unbiased evidence for the efficacy and safety of somatropin therapy in Noonan syndrome will come from appropriately controlled studies of sufficiently large numbers of patients defined on such a basis and followed to final height. This is now possible but will require international cooperation. Nevertheless, the clinical relevance of somatropin therapy in Noonan syndrome and other short stature syndromes will be dependent on looking beyond improvement in final height (even if achievable) to psychological and quality of life outcomes.