Distinct functions for thyroid hormone receptors alpha and beta in brain development indicated by differential expression of receptor genes

Thyroid hormones are essential for correct brain development, and since vertebrates express two thyroid hormone receptor genes (TR alpha and beta), we investigated TR gene expression during chick brain ontogenesis. In situ hybridization analyses showed that TR alpha mRNA was widely expressed from early embryonic stages, whereas TR beta was sharply induced after embryonic day 19 (E19), coinciding with the known hormone-sensitive period. Differential expression of TR mRNAs was striking in the cerebellum: TR beta mRNA was induced in white matter and granule cells after the migratory phase, suggesting a main TR beta function in late, hormone-dependent glial and neuronal maturation. In contrast, TR alpha mRNA was expressed in the earlier proliferating and migrating granule cells, and in the more mature granular and Purkinje cell layers after hatching, indicating a role for TR alpha in both immature and mature neural cells. Surprisingly, both TR genes were expressed in early cerebellar outgrowth at E9, before known hormone requirements, with TR beta mRNA restricted to the ventricular epithelium of the metencephalon and TR alpha expressed in migrating cells and the early granular layer. The results implicate TRs with distinct functions in the early embryonic brain as well as in the late phase of hormone requirement.

Contrasting developmental and tissue-specific expression of alpha and beta thyroid hormone receptor genes

Thyroid hormones and their receptors (TRs) have critical functions in development. Here we show that a chicken TR beta cDNA clone encodes a receptor with a novel, short N-terminal domain. In vitro-expressed TR beta protein bound thyroid hormone with similar affinity as the chicken TR alpha. Comparison of expression of TR alpha and TR beta mRNAs throughout chicken development until 3 weeks post-hatching revealed ubiquitous expression of TR alpha mRNAs (in 14 different tissues) with some variations in levels, from early embryonic stages. In contast, expression of TR beta mRNA was restricted, occurring notably in brain, eye, lung, yolk sac and kidney, and was subject to striking developmental control, especially in brain where levels increased 30-fold upon hatching. Levels also sharply increased in late embryonic lung, but were relatively high earlier in embryonic eye and yolk sac. RNase protection analyses detected no obvious mRNAs for alpha and beta TRs with variant C-termini as demonstrated previously for the rat TR alpha gene. The data suggest a general role for TR alpha and specific developmental functions for TR beta, and that thyroid-dependent development involves temporal and tissue-specific expression of the TR beta gene.

Requirement for the C-terminal domain of the v-erbA oncogene protein for biological function and transcriptional repression

In contrast to the normal thyroid hormone receptor, the v-erbA product fails to bind hormone due to mutations in the C-terminal ligand binding domain and thus appears to represent a hormone-independent, oncogenic transcription factor. Therefore, we asked whether or not the C-terminal domain of v-erbA is required for its biological activity and putative transcriptional control functions by analysing mutants with altered C-termini. A v-erbA protein truncated in the C-terminal domain lacked detectable biological activity in transformed erythroblasts and its transcriptional repression function with respect to the band 3 gene was abolished. The protein displayed a nuclear location and could still bind to DNA, indicating that the N-terminal region retained DNA-binding activity but was insufficient to produce characteristic v-erbA changes in erythroblasts. Another biologically defective v-erbA variant with a small frameshift towards the extreme C-terminus also failed to repress band 3, indicating a requirement for a specific C-terminal structure in repression. However, this mutant retained partial biological activity, stimulating erythroblasts to grow at a higher rate than cells containing a completely inactive, deleted v-erbA gene. The results demonstrate that the mutated hormone-binding domain, in addition to the DNA-binding region, is critical for v-erbA biological and transcriptional control functions.

The experience of caring

Caring is inextricably bound to the belief system and practice of nursing. Yet there is a lack of research on what caring is for the practising nurse. It was the purpose of this qualitative study to investigate the phenomenon of caring with 17 hospital staff nurses who, in taped sessions, described their subjective experiences of caring. Phenomenology, an inductive descriptive research method, was used with the data analysed according to Colaizzi's procedure. Thirty theme clusters, emerging from specific themes, fell into seven categories under two broad classifications; 'what is caring' and 'what affects caring'. The essential structure of caring is described and implications for nursing education, practice and research discussed.

MAL63 codes for a positive regulator of maltose fermentation in Saccharomyces cerevisiae

Genetic analysis of the MAL6 locus has previously yielded mal6 mutants which fall into a single complementation group and which are noninducible for maltase and maltose permease. However, the strains used in these studies contained additional partially functional copies of MAL1 (referred to as MAL1g) and MAL3 (referred to as MAL3g). Using a strain lacking MALg genes, we have isolated two classes of mutants and these classes correspond to mutations in MAL63 and MAL61, two genes of the MAL6 complex. Disruptions of MAL63 are noninducible for maltase and maltose permease and for their corresponding mRNAs. The mal6 mutants are shown to map to MAL63. Inducer exclusion as a cause of the noninducible phenotype of the mal63 mutations has been eliminated by constructing a mal63 mutant in a strain constitutive for maltose permease; the strain remains noninducible. These results rigorously demonstrate that MAL63 is a regulatory gene which plays a positive role in the regulation of maltose fermentation.

Recombinant feline viruses containing the myc gene rapidly produce clonal tumours expressing T-cell antigen receptor gene transcripts

We, and others, have recently shown that recombinant feline leukaemia viruses (FeLV) containing the myc gene (FeLV-myc) occur in up to 30% of naturally occurring cases of T-cell lymphosarcoma. Investigation of the disease spectrum of two FeLV-myc isolates showed that they induced clonal or oligoclonal T-cell tumours after a short latent period. The phenotypic pattern of the thymic tumours was restricted in that they all expressed the alpha and beta chains of the T-cell antigen receptor and could readily be established in culture in vitro without the addition of exogenous interleukin-2. Although helper FeLV was transmitted from infected cats to uninfected tracer cats, there was no evidence of horizontal transmission of FeLV-myc viruses, suggesting that these viruses arise de novo in individual cases of thymic lymphosarcoma.

Altered structure and expression of c-myc in feline T-cell tumours

The c-myc gene is rearranged in a subset of feline T-cell lymphosarcomas. Detailed mapping of c-myc rearrangements showed that some result from feline leukaemia virus (FeLV) proviral integration within or upstream of c-myc, but one case involves a complex 3' alteration and amplification which is apparently not directly virus-induced. S1 nuclease mapping of RNA from normal cells using c-myc probes revealed two presumptive 5' ends, each corresponding to a promoter-like sequence (P1 and P2), and a major 3' discontinuity which mapped to the 3'-most of two possible polyadenylation signals. Analysis of RNA from a series of tumours revealed different modes of c-myc expression. All tumours produced P1 and P2 transcripts with apparently normal structure except for one case where an insertion in intron 1 displaced exon 1 sequences. The abundance ratio of P1/P2 transcripts varied considerably and was high in tumours which carry a rearrangement adjacent to c-myc, but some other T-cell tumours with no apparent myc alteration displayed an equally high ratio. However, a consistent feature was the lack of detectable RNA from normal c-myc alleles in tumours which express a rearranged c-myc allele or a transduced FeLV v-myc gene. We suggest that this may prove to be a useful indicator of the presence of an oncogenically active myc gene, whether this is a rearranged c-myc or transduced v-myc sequence.

Retroviral transduction of T-cell antigen receptor beta-chain and myc genes

Support for multistage models of oncogenesis has been provided by several highly leukaemogenic retrovirus isolates that have transduced more than one host cell gene. Where functional studies have been performed, these retroviral oncogenes show synergy for in vitro transformation and leukaemogenesis. In naturally occurring feline leukaemias associated with feline leukaemia virus (FeLV), retroviral transduction of myc is a frequent oncogenic mechanism. But evidence suggesting that the FeLV v-myc genes might be insufficient for leukaemogenesis was provided by the latency (12 weeks) and clonality of FeLV/v-myc-induced tumours and the absence of demonstrable in vitro transformation by these viruses. In the search for secondary leukaemogenic events in FeLV/v-myc tumours, we have identified a case of FeLV transduction of a T-cell antigen receptor beta-chain gene. The proviruses carrying this gene (which we have named v-tcr) were a separate population from those carrying v-myc. In its normal role, the T-cell receptor beta-chain forms part of a multimeric complex involved in antigen recognition and T-cell activation. We suggest that v-tcr is a novel viral oncogene which assisted v-myc in the genesis of a naturally occurring case of thymic lymphosarcoma.

Smoke from laser surgery: is there a health hazard?

The composition of plume produced during carbon dioxide laser endoscopic treatment for endometriosis was examined to determine whether it represented a hazard to the surgical staff. A total of 32 plume samples were collected from 17 women undergoing laser laparoscopic treatment for endometriosis and/or adhesions. The smoke was found to consist of particles having a median aerodynamic diameter of 0.31 micron with a range of 0.10-0.80 micron. The size range has two consequences: 1) using a human red blood cell as a model for all cells, it can be stated with greater than 99.9999% certainty that no cell-size particles, including cancer cells, are present in the plume; 2) particles in this size range are too small to be effectively filtered by currently available surgical masks.

Conservation of the c-myc coding sequence in transduced feline v-myc genes

We have cloned the normal feline c-myc locus and determined the nucleotide sequence of all three exons. The feline c-myc gene shows close homology to other mammalian c-myc genes, particularly human c-myc. The feline and human sequences are colinear within the open reading frame for the putative c-myc product but show insertions and deletions relative to each other outside this domain. We have also analyzed a cloned FeLV provirus, CT4, which contains the host-derived myc gene. In this provirus the v-myc sequences are located at the 3' end of the pol gene, replacing pol and env sequences. Nucleotide sequence analysis of CT4 shows an open reading frame for a v-myc gene product which may be expressed without fusion to any viral protein sequences. This contrasts with another FeLV v-myc (LC), in which myc and gag sequences were found to be fused. Unlike previously identified avian v-myc genes, the feline v-myc genes contain exon 1-derived sequences, but these have been truncated or internally deleted. The FeLV CT4 v-myc sequence shows very few coding changes relative to c-myc and the FeLV LC v-myc coding sequence is unchanged relative to c-myc apart from fusion to gag. These results are discussed in relation to the mechanism of transduction and activation of myc by FeLV.

Long-term effects of nonorganic failure to thrive

Fourteen children admitted to the hospital at an average age of 12.5 years previously were reviewed in comparison with a group of children matched for age, sex, social class, and ethnic group. The children in the study group were smaller in height and weight, than children in the comparison group. They had lower scores on the verbal intelligence scale of the Wechsler Intelligence Scale for Children--Revised, poorer language development, and less well-developed reading skills. They had lower social maturity and a higher incidence of behavioral disturbances. There were no differences between the study and comparison groups in family size, maternal age, family health, social isolation, and mothers' childhood experiences. The study group mothers had less knowledge about their children's education, were more anxious, and had a tendency toward concrete thinking. To prevent the long-term adverse effects of nonorganic failure to thrive, a more active, practical, and long-term program, begun at the time of presentation, is recommended.

Mothers of abused children. A comparison study

A group of 36 mothers whose children had suffered from child abuse at an average of 5 1/2 years previously was compared with a group of mothers of similar social class where there had been no reported instances of abuse of their children. There was no significant difference between the two groups with regard to marital, housing, or financial problems or in physical health. Statistically significant differences were found between the abuse and comparison group mothers in the following areas: the abuse group mothers (1) were less likely to have been brought up by their own parents; (2) had more negative feelings towards their fathers; (3) were more likely to have received help for an emotional disorder; (4) had higher expectations for their children; (5) perceived a greater number of personality problems in their children; and (6) were more likely to have assertive, demanding, and suspicious personality traits. It is possible that these maternal factors will influence the emotional development of their children.

The development of abused children

Thirty-nine children were reviewed who had suffered child abuse at an average of 5 1/2 years earlier. In comparison with a group matched for socio-economic status, the abused children performed significantly lower on the Wechsler Intelligence Scale, and were more delayed in language development and reading ability. Their teachers' assessments of behaviour showed significantly more abnormal profiles than in the comparison group. These differences could not be accounted for by the small proportion of known head-injuries in the abused group. Child abuse has long-term effects, so it is necessary that these children are thoroughly assessed at first presentation, and that they are followed with a specific programme aimed at preventing these sequelae.

Reliability of mothers' reports of birth data

To determine the reliability of recall of birth and early childhood events, a group of 47 mothers was asked details of their child's birth and about any child-rearing problems at an average of 5-6 years after the birth. Thirty-four of these mothers were asked similar questions 3 years later. The information given by the mothers was compared with the information documented in the hospital records when the children were born. The mothers overestimated the length of pregnancy and overestimated the number of neonatal problems. Only half could recall the birth weight accurately. When asked the same questions 3 years later there was a tendency for memory to have mellowed with fewer pregnancy complications and child-rearing difficulties being recalled than on the previous interview. Information given by mothers about such objective data as length of gestation, birth weight and obstetric complications is not necessarily accurate. Less objective data may be recalled even less accurately.

Development in children following abuse and nonorganic failure to thrive

Thirty-nine children who had been abused an average of 5 1/2 years earlier and 14 children who had been admitted to the hospital with nonorganic failure to thrive (NOFTT) 13 years earlier were studied to look at similarities and differences in their development. Each group was studied in relation to a comparison group matched for age, sex, social class, and ethnic background. The abused children and those with NOFTT were similar in their language ability, and were significantly behind their comparison groups in language development, reading age, and verbal intelligence. The abused children, but not the group who had NOFTT, were significantly behind their comparison group in general intelligence, interpersonal relations, and self-concept, but in contrast to the children with NOFTT they were not delayed in social maturity. The long-term adverse sequelae of these two conditions emphasize the need for a long-term, child-centered approach.

Persisting characteristics of parents of battered children

To study the personality of mothers whose children had suffered from child abuse in the past, a group of 36 such mothers was compared with a control group of mothers matched for social class. There was no difference between the two groups in pregnancy experience, in general health or in the number of family problems they had. The mothers from the study group had higher expectations for their children and perceived their children as having more personality problems than did the control mothers. The study-group mothers were less likely to have been brought up by their own parents, had more negative feelings towards their fathers, and were more likely to have received help for an emotional disorder than the control mothers. On formal testing, they were more likely to have suspicious, assertive, and demanding personality characteristics. As the majority of abused children remain in their natural families, these maternal factors are likely to influence the emotional development of their children. The children, as well as the parents, from families where child abuse has occurred should receive long-term supportive treatment to try to ameliorate some of the effects of these parental characteristics.