Migration of enteric neural crest cells in relation to growth of the gut in avian embryos

Neural crest cell migration in the gut and the growth of the mid- and hindgut of avian embryos was investigated by a combination of whole-mount immunofluorescence of the HNK-1 neural crest marker epitope, chorioallantoic membrane grafting and morphometry. HNK-1-labelled cells advanced rostrocaudally in the gut of quail embryos (to the duodenum by stage HH 21, to the umbilicus by HH 25, to the ceca by HH 27, to the cloaca by HH 33). The timetable in chick embryos appeared to be slightly slower, but neural cells were obscured by background fluorescence in this species. More rostral regions of the gut commenced rapid growth earlier than more caudal regions (preumbilical small intestine after HH 26, postumbilical small intestine after HH 27 and colorectum after HH 28), and the small intestine and ceca grew most rapidly in length while the colorectum grew most rapidly in diameter. The rates of growth of the gut were low prior to the stage when HNK-1-labelled cells normally arrive in the small intestine, ceca and rostral colorectum, but increased dramatically after arrival. In the caudal colorectum rapid growth had commenced at the time of arrival of these cells. These data are consistent with the idea that a delay in arrival of vagal neural crest cells at any point in the intestine could jeopardize the ability of the cells to fully populate the remainder of the gut, due to the normal growth spurt causing the migration end-point to recede faster than the rate of neural crest cell migration. Thus, a mismatch in timing of neural crest cell migration and gut growth could play a role in the etiology of some forms of Hirschsprung's disease.

Hlx homeo box gene is essential for an inductive tissue interaction that drives expansion of embryonic liver and gut

The divergent murine homeo box gene Hlx is expressed in restricted hematopoietic cell types and, during embryogenesis, prominently in visceral mesenchyme of the developing liver, gall bladder, and gut. Targeted disruption of the gene has now established that it plays a key role in visceral organogenesis. Embryos homozygous for the mutation died around embryonic day 15 with anemia and severe hypoplasia of the liver and gut. Liver ontogeny commenced normally with formation of the liver diverticulum and differentiation of hepatocytes, but the organ failed to expand and reached only 3% of normal size. The apparent liver hypoplasia was not associated with a notable increase in apoptotic cells. Gut development also began normally, but the intestines failed to undergo extensive elongation and looping and reached only a quarter of normal length. The anemia resulted from a deficiency in the fetal form of hematopoiesis, which occurs in the liver, but no intrinsic defect in Hlx-/- hematopoietic cells was observed in vitro, and liver-derived Hlx-/- hematopoietic stem cells that were transplanted to irradiated normal mice could fully reconstitute hematopoiesis. The impaired fetal hematopoiesis therefore reflects insufficient support function provided by the minute liver. Hlx is normally expressed in visceral mesenchyme lying adjacent to the developing liver and gut epithelia affected by the mutation, but not in the epithelia themselves. Hence, Hlx regulates a mesenchymal-epithelial interaction that drives a vital growth phase in visceral organogenesis. Moreover, because mutation of Hlx blocked liver growth but not its specification, early morphogenesis, or differentiation, development of this organ appears to occur by step-wise inductive interactions under separate genetic control.

Absence of yolk sac hematopoiesis from mice with a targeted disruption of the scl gene

The scl gene encodes a basic-helix-loop-helix transcription factor which was identified through its involvement in chromosomal translocations in T-cell leukemia. To elucidate its physiological role, scl was targeted in embryonic stem cells. Mice heterozygous for the scl null mutation were intercrossed and their offspring were genotyped. Homozygous mutant (scl-/-) pups were not detected in newborn litters, and analysis at earlier time points demonstrated that scl-/- embryos were dying around embryonic day 9.5. The scl-/- embryos were pale, edematous, and markedly growth retarded after embryonic day 8.75. Histological studies showed complete absence of recognizable hematopoiesis in the yolk sac of these embryos. Early organogenesis appeared to be otherwise normal. Culture of yolk sac cells of wild-type, heterozygous, and homozygous littermates confirmed the absence of hematopoietic cells in scl-/- yolk sacs. Reverse transcription PCR was used to examine the transcripts of several genes implicated in early hematopoiesis. Transcripts of GATA-1 and PU.1 transcription factors were absent from RNA from scl-/- yolk sacs and embryos. These results implicate scl as a crucial regulator of early hematopoiesis.

Myogenic and morphogenetic defects in the heart tubes of murine embryos lacking the homeo box gene Nkx2-5

The murine homeo box gene Nkx2-5 is expressed in precardiac mesoderm and in the myocardium of embryonic and fetal hearts. Targeted interruption of Nkx2-5 resulted in abnormal heart morphogenesis, growth retardation and embryonic lethality at approximately 9-10 days postcoitum (p.c.). Heart tube formation occurred normally in mutant embryos, but looping morphogenesis, a critical determinant of heart form, was not initiated at the linear heart tube stage (8.25-8.5 days p.c.). Commitment to the cardiac muscle lineage, expression of most myofilament genes and myofibrillogenesis were not compromised. However, the myosin light-chain 2V gene (MLC2V) was not expressed in mutant hearts nor in mutant ES cell-derived cardiocytes. MLC2V expression normally occurs only in ventricular cells and is the earliest known molecular marker of ventricular differentiation. The regional expression in mutant hearts of two other ventricular markers, myosin heavy-chain beta and cyclin D2, indicated that not all ventricle-specific gene expression is dependent on Nkx2-5. The data demonstrate that Nkx2-5 is essential for normal heart morphogenesis, myogenesis, and function. Furthermore, this gene is a component of a genetic pathway required for myogenic specialization of the ventricles.

Extracellular matrix and adhesive molecules in the early development of the gut and its innervation in normal and spotting lethal rat embryos

The distribution of fibronectin (FN), laminin (LM), J1/tenascin, chondroitin sulphate proteoglycan (CSPG), neural cell adhesion molecule (NCAM), neurofilament (NF) and the HNK-1 epitope were studied immunohistochemically in the developing mid- and hindgut of E12.5-E16.5 rat embryos. Over this period the gut wall changed from a uniform mesenchyme to an annular organisation. FN and LM remained widely distributed, but J1/tenascin became concentrated in mesenchyme outside the nascent circular muscle layer, and CSPG declined in, and NCAM increased in, the circular layer. Protease and fixation treatments suggested that CSPG could mask other molecules such as LM. This re-organisation proceeded bidirectionally, as a rostrocaudal wave which was met in the colon by a caudorostral wave. The caecum, however, was conspiciously delayed in all maturation events and also showed mesenchymal and serosal epithelial labelling for the cell-adhesion-related HNK-1 epitope, which was absent elsewhere. This period also covered the appearance of enteric neurons, recognised by HNK-1 and NF antibodies. Cells labelled by these antibodies appeared in a unidirectional rostrocaudal wave, from the duodenum at E12.5 to the rectum at E16.5. This wave was not in exact synchrony with the wave of intestinal maturation, but lagged behind so that neuronal cells first appeared in increasingly mature micro-environment at progressively more caudal levels. These cells initially were positioned imprecisely about mid-way across the gut mesenchyme layer and were not clearly related spatiotemporally to any of the above molecules. Slightly later, however, this neural region was broadly defined by relatively low levels of both CSPG and J1/tenascin. The final position of the myenteric neurons was very precise, and was related to a thin J1/tenascin layer and to a step in NCAM labelling intensity. Litters of pups, of which 25% would be expected to be spotting lethal homozygous embryos which develop total colonic and caecal aganglionosis, showed no difference in any of the molecules studied, but in 4 embryos out of 12, the progress of the rostrocaudal wave of neuron appearance was distinctly slowed even in the duodenum and proximal small intestine, regions well outside the final aganglionic zone. The observations suggest that this Hirschsprung's-disease-like regionalised defect is a result of a generalised abnormality which does not involve gross changes in extracellular matrix and NCAM expression.

Nkx-2.5: a novel murine homeobox gene expressed in early heart progenitor cells and their myogenic descendants

We have isolated two murine homeobox genes, Nkx-2.5 and Nkx-2.6, that are new members of a sp sub-family of homeobox genes related to Drosophila NK2, NK3 and NK4/msh-2. In this paper, we focus on the Nkx-2.5 gene and its expression pattern during post-implantation development. Nkx-2.5 transcripts are first detected at early headfold stages in myocardiogenic progenitor cells. Expression preceeds the onset of myogenic differentiation, and continues in cardiomyocytes of embryonic, foetal and adult hearts. Transcripts are also detected in future pharyngeal endoderm, the tissue believed to produce the heart inducer. Expression in endoderm is only found laterally, where it is in direct apposition to promyocardium, suggesting an interaction between the two tissues. After foregut closure, Nkx-2.5 expression in endoderm is limited to the pharyngeal floor, dorsal to the developing heart tube. The thyroid primordium, a derivative of the pharyngeal floor, continues to express Nkx-2.5 after transcript levels diminish in the rest of the pharynx. Nkx-2.5 transcripts are also detected in lingual muscle, spleen and stomach. The expression data implicate Nkx-2.5 in commitment to and/or differentiation of the myocardial lineage. The data further demonstrate that cardiogenic progenitors can be distinguished at a molecular level by late gastrulation. Nkx-2.5 expression will therefore be a valuable marker in the analysis of mesoderm development and an early entry point for dissection of the molecular basis of myogenesis in the heart.

Age-related changes in oral sensation

Oral sensation (including two-point discrimination, oral stereognosis, vibrotactile detection, somesthetic sensitivity, proprioception, and thermal sensitivity) was studied in 60 healthy adults in five age categories: 20 to 34, 35 to 49, 50 to 64, 65 to 79, and 80 years and above. Thermal and somesthetic sensitivity as well as proprioception did not change with age. Ability to differentiate tactile and vibratory sensation on the lip decreased after age 80 (P less than .01), but vibration detection on the soft palate did not change. Stereognostic ability remained good up to age 80, and then declined for four of the nine shapes tested (P less than .01). Two-point discrimination deteriorated on the upper lip (P less than .01), on the cheeks (P less than .02), and on the lower lip (P less than .06). Two-point discrimination on the tongue and palate did not change. It was noted that oral sensation remained good with aging, showing only a slight decline in function after age 80.

Post-choledochoenterostomy 'sump syndrome'

The 'sump syndrome' is an uncommon, late complication of a side-to-side choledochoenterostomy. Five patients with this syndrome were encountered over a 5-year period. Pain or cholangitis was the clinical presentation in four patients, whereas one patient presented with secondary septic arthritis and a hepatic abscess. Liver function tests were mildly abnormal in each patient. All patients had a stomal size of less than 1 cm as assessed by forward- or side-viewing endoscopy. Endoscopic retrograde cholangiography revealed either stones or debris in the distal common bile ducts of all patients. Four patients had a surgical clearance of their duct with concurrent closure of the choledochoduodenostomy in three patients and the creation of a Rouxen-Y end-to-side choledochojejunostomy in the fourth patient. The other patient had an endoscopic sphincterotomy performed. After 1-4 years of follow-up, four patients have had a total resolution of symptoms. The other patient with follow-up for 4 years has had one episode of cholangitis which resolved rapidly with antibiotic treatment. The pathogenesis and clinical spectrum of the sump syndrome are reviewed and current management strategies are discussed.

Hierarchy of cytotoxic T cell clones. I. Reversal of resistance to lysis and killing between anti-hapten cytotoxic T cells

Cells from clones of anti-hapten cytotoxic T lymphocytes (CTL) can act as both effector cells and, when treated with the specific hapten, as target cells. Individual clones can kill haptenated cells only from other clones that are less efficient killers. Clones specific for both fluorescein and trinitrophenol could be ordered in a single hierarchy in which resistance to lysis correlated with lytic efficiency. When the killing efficiency was reduced with phorbol myristate acetate (PMA) or the colchicine analogue, Colcemid, the degree of resistance to lysis was also reduced. The use of PMA-treated fluoresceinated targets greatly enhanced intraclonal killing and similarly lead to a repositioning of clones within the hierarchy of normal cells. By the haptenation of appropriate clones, efficient CTL could kill cells from other clones in a direction apparently opposite to recognition. The results demonstrate that effects other than antigen recognition of the target cell may result in variations in the nature of T cell immune responses.

Hierarchy of cytotoxic T cell clones. II. Intraclonal triggering of lysis by hapten-specific CTL

Cells from clones of anti-hapten murine cytotoxic T lymphocytes (CTL) can act as both target and effector cells, but will not lyse members of the same clone. The effect of haptenation on the cytolytic activity of anti-fluorescein (FL) and anti-trinitrophenol (TNP) CTL clones was examined. Treatment of anti-FL clones with fluorescein isothiocyanate or anti-TNP clones with trinitrobenzene sulphonic acid induces these clones to kill in an antigen-independent fashion. Targets killed by the haptenated CTL included syngeneic and allogeneic B lymphocyte blast cells, P815, YAC-1 and in one case human GM 4072 tumor cells. The importance of CD8 and T cell receptor (TCR) occupancy is demonstrated by the ability to block autotriggering by antibody directed against Ly 2 and the TCR. The results demonstrate that effects other than antigen recognition of the target play a role in the final outcome of effector-target cell interactions and provide a mechanism which could lead to autodestruction and immunosuppression particularly in some types of viral infection.

Hypertrophy of radial and ulnar arteries following denervation of the chicken wing

Denervation of radial and ulnar arteries in the growing and adult domestic fowl was achieved by unilateral sectioning of the brachial plexus. Eight weeks later the denervated arteries and those of the contralateral wing were examined with light- and electron microscopy to determine the effect of denervation on arterial structure. In growing fowls, the area of the media in radial and ulnar arteries was increased by 29% and 25%, respectively, after denervation. The number of smooth muscle layers was also significantly increased by 16% (radial) and 14% (ulnar), but no significant variation was seen in the wall/lumen ratio of either growing artery. In adult fowls, the area of the media was increased by 93% (radial) and 32% (ulnar) following denervation and the number of smooth muscle cell layers increased by 39% (radial) and 11% (ulnar). There was also an increased wall/lumen ratio of 64% (radial) and 92% (ulnar). These results indicate that hyperplasia of smooth muscle has occurred in response to denervation. Flow-cytometric DNA analysis of growing arteries also indicates that the increase in muscle-cell volume is a result of cell division (not polyploidy) since no significant differences were found between the control and denervated arteries in any stages of the cell cycle.

Differentiated thyroid carcinoma, intermediate type

A thyroid carcinoma showing histological and histochemical features of both follicular and parafollicular cell carcinoma was diagnosed in a 56 year old male. Previously the two cell types have been considered to be derived from embryologically distinct and separate precursors. The unusual combination of the two cell types in this tumour suggests the possibility that the cell lines may be derived from a common stem cell with the potential of differentiating into both follicular and parafollicular cells. The tumour was aggressively invasive and had metastasized widely to lymph nodes at the time of presentation. It represents an example of the recently described entity of differentiated thyroid carcinoma of intermediate type.

Hyperactivity, drugs and attention to features in a story

Twenty hyperactive children were divided into two groups of 10 volunteers. Group 1 was taken off its medication (methylphenidate) for two weeks and group 2 was kept on its medication at the usual dosage. About one week following the cessation of medication subjects from both groups heard a story and were shown some pictures illustrating events in the story. They were then tested on their memory for this material. One week later their delayed retention was tested. Both immediate and delayed retention was better in those children who remained on medication. This was especially true for the incidental material.

Difficulties in the endoscopic diagnosis of gastric and oesophageal cancer

A study was made of 116 patients with gastric or oesophageal cancer, in whom endoscopy was negative, or biopsy was negative or not performed. The most common problems were the presence of pyloric or oesophageal stricture (sometimes with excessive luminal content) and difficulty in obtaining diagnostic biopsy material in linitis plastica, early gastric cancer, lymphoma and sarcoma. Problems also occurred from failure to biopsy apparently benign conditions and from delay in a second endoscopy. Some cancers were regarded as benign ulcers and treated as such by drugs or surgery because more reliance was placed on endoscopic biopsy than on the endoscopist's opinion of the macroscopic appearance. In 17 of the 16 patients there was delay, incorrect management or further difficulty in diagnosis.

Morbidity and mortality of operative intubation for malignant oesophageal obstruction

In 33 patients who underwent operative intubation of carcinoma of the oesophagus or gastric cardia, there were nine postoperative deaths (mortality 27%). Only 15 patients (46%) had no further operative procedure or anaesthetics, but their mean survival was only 3.7 months. Nine patients (27%) required a total of 17 procedures after the placement of their original tube. Operative intubation has a similar mortality to resection but the survival times are short. Whenever possible palliative resection or endoscopic intubation is to be recommended.

Phaeochromocytoma in Queensland--1970-83

A statewide survey was conducted in Queensland to record all cases of phaeochromocytoma between the years of 1970 and 1983 inclusive. There were 46 cases giving an incidence of 1.55/million population per year. Twenty-nine patients (63%) were successfully treated while 10 patients (22%) died of the tumour effects. Seven cases (15%) were found incidentally at autopsy, though at least one showed diagnostic clinical features before death. Five patients (11%) had extra adrenal phaeochromocytoma, five patients (11%) had multiple tumours, four patients (9%) had multiple endocrine neoplasia and three patients (7%) had clinically malignant tumours. Of 13 patients suffering a major adrenergic crisis only six survived. Five patients with unsuspected phaeochromocytoma suffered crisis under anaesthesia and only one survived. Only one of the patients dying of benign phaeochromocytoma had adequate ante mortem adrenergic blockade. Of all patients in the series 35% were not diagnosed in life.

Early gastric cancer

Thirty patients with early gastric cancer were studied as part of a consecutive series of 308 gastric cancers, giving a proportion of 9.7%. Twenty-eight of the early gastric cancer patients were symptomatic, pain being the most common symptom. Endoscopy proved more effective than barium studies as a first investigation but the diagnosis rate at first examination was still only 69%. Seven patients with early gastric cancer had lymph node spread at the time of presentation. Five patients eventually died of cancer metastases. There was a high incidence of benign peptic ulceration (50%) and this with lymph node metastasis was an unfavourable prognostic feature. Only four of the 26 patients submitted to standard surgical resections died of cancer. This study supports the concept that early gastric cancer does indeed occur in Western man and the five year survival rate (65%) is much higher than for late gastric cancer (13%). The high incidence of metastasis at the time of presentation may account for the difference between our survival rate for early gastric cancer, and that reported from Japan.

Selective inhibition by NPT 15392 of lymphocyte cyclic GMP phosphodiesterase

Cyclic nucleotide phosphodiesterases were measured in mouse spleen and thymus lymphocyte membranes and soluble fractions and in extracts of canine tracheal smooth muscle. The immunostimulant erythro-9(2-hydroxy,3-nonyl) hypoxanthine (NPT 15392) was found to be a potent and relatively selective inhibitor of mouse lymphocyte cyclic GMP phosphodiesterase, with IC50 values 15-180 times greater for cyclic AMP than cyclic GMP phosphodiesterases. The greatest inhibition by NPT 15392 was found using 10 microM substrate, and inhibition was greater in membrane than soluble forms of phosphodiesterase. Spleen soluble enzymes were separated by DEAE Bio-Gel A column into six peaks. A major form of cyclic GMP phosphodiesterase was inhibited effectively by NPT 15392 in a competitive manner (Ki = 50 microM). Cyclic AMP phosphodiesterase activity in the same fraction, but representing only a fifth of the total activity, was also inhibited (Ki = 70 microM). Other soluble enzymes were not affected significantly. Membrane bound enzymes were solubilized and separated into three peaks. One with high affinity for cyclic GMP was strongly inhibited (Ki = 10 microM) by NPT 15392. Inosine and isoprinosine were one-tenth to one-hundredth as effective as NPT 15392 as cyclic nucleotide phosphodiesterase inhibitors. Incubation of mouse splenic lymphocytes with NPT 15392 for 48 hr resulted in enzymes with altered responsiveness to the drug in broken cell assays: inhibition of cyclic GMP hydrolysis was enhanced while that of cyclic AMP hydrolysis was decreased. Among three separated and characterized forms of tracheal smooth muscle phosphodiesterase, NPT 15392 inhibited the low Km cyclic GMP phosphodiesterase 6-10 times more effectively than the other enzymes. These data suggest that the immunopharmacologic activities of NPT 15392 may include specific cyclic GMP phosphodiesterase inhibition as one of several possible mechanisms.

Hyperactivity, drugs and attention deficit

Thirty-two hyperactive children who were under imipramine or methylphenidate medication took part in the experiment. The children were asked to learn a set of paired associate pictures containing a salient, central, figure and a secondary figure below. Free recall of all pictures was scored both immediately and seven days later. The children were subdivided into four groups according to the classical state-dependent learning paradigm. Group 1 was withdrawn from medication on both trials, groups 2 and 3 were withdrawn from medication on the first or second trial and group 4 received medication on both trials. No drug effects were found in immediate total recall. Delayed free recall was improved when original learning was under the drug state. This result was related to the proposal that arousing words are better remembered in delayed recall. Delayed recall of the secondary stimuli was particularly improved by the drugs during learning. Drug state dependency of the children's memory was also shown.

Toxic adenoma in childhood--case report

A 12-year-old girl was noted to have a left sided thyroid nodule on routine examination. Although clinically euthyroid she was found to have an elevated T3 value, and the TSH failed to rise following TRH injection. Thyroid scan showed a hyperfunctioning nodule in the left lobe of the thyroid gland. Following surgical removal of the nodule the patient became biochemically euthyroid and a repeat thyroid scan demonstrated the previously suppressed normal right lobe.

Carcinoma of the oesophagus

A survey of carcinoma of the oesophagus at Kalafong Hospital revealed a greater incidence of the disease in males, being highest in the age group 50 - 59 years, with the middle third of the oesophagus the most prevalent site and with oesophagotracheal or oesophagobronchial fistulae a common complication.

Paradoxical effects in sleep and performance of two doses of chlorpromazine

Twenty-four subjects were given placebo, 25 mg, and 75 mg of chlorpromazine on three separate occasions. Twelve subjects were treated in the morning and tested for performance during the day. Twelve other subjects received the drug treatments in the evening. Both groups had their EEG stages of sleep recorded during the subsequent night. The low dose of drug shortened the REM/non-REM cycle length in comparison to the high dose, and placebo values were intermediate. In performance tests, visual integration time was impaired by the high dose of the drug. Logical reasoning was slowed by the high dose of the drug in comparison to the low dose, with placebo values intermediate between the two.

Chlorpromazine and serial reaction performance

The effect of 25 mg or 75 mg of chlorpromazine on the serial reaction performance of 12 male human subjects was studied. Speed or number of correct responses was reduced by the high dose of chlorpromazine and errors of commission and omission were increased. The adverse effect of the drug upon speed appeared only at the end of the half-hour test. By contrast the adverse effect upon gaps and errors was apparent throughout the test and there was no interaction with test duration.

Behavioural antagonism between chlorpromazine and noise in man

The effects of 25 mg and 75 mg of chlorpromazine and of 95 dBA of white noise were studied separately and together in 12 male human subjects. Performance, analysed by signal detection theory, showed that both noise and chlorpromazine applied separately caused impairment in similar ways. Suspended judgements were reduced and negative decisions correspondingly increased at low levels of evidence. When applied together, chlorpromazine and noise cancelled out each other's adverse effects. It is concluded that chlorpromazine is a specific behavioural antagonist of the stressful effects of noise.