A SYNTHETIC FOOD MEDIUM FOR THE CULTIVATION OF DROSOPHILA : PRELIMINARY NOTE

In this paper is described the composition and method of making a standard synthetic medium for the laboratory cultivation of Drosophila melanogaster. It is shown that this medium is greatly superior to the banana medium commonly used for this purpose in respect of both the fertility and the mortality of flies kept on it. The range of superiority in respect of fertility is at different densities of population from about 48 per cent at the lowest, to 98 per cent at the highest densities experimentally reported here. The general experience of the laboratory with this medium, which frees experimental work on Drosophila from the incubus of the highly variable banana, shows it to have other points of superiority besides those discussed here.

Weaning from mechanical ventilation

Weaning covers the entire process of liberating the patient from mechanical support and from the endotracheal tube. Many controversial questions remain concerning the best methods for conducting this process. An International Consensus Conference was held in April 2005 to provide recommendations regarding the management of this process. An 11-member international jury answered five pre-defined questions. 1) What is known about the epidemiology of weaning problems? 2) What is the pathophysiology of weaning failure? 3) What is the usual process of initial weaning from the ventilator? 4) Is there a role for different ventilator modes in more difficult weaning? 5) How should patients with prolonged weaning failure be managed? The main recommendations were as follows. 1) Patients should be categorised into three groups based on the difficulty and duration of the weaning process. 2) Weaning should be considered as early as possible. 3) A spontaneous breathing trial is the major diagnostic test to determine whether patients can be successfully extubated. 4) The initial trial should last 30 min and consist of either T-tube breathing or low levels of pressure support. 5) Pressure support or assist-control ventilation modes should be favoured in patients failing an initial trial/trials. 6) Noninvasive ventilation techniques should be considered in selected patients to shorten the duration of intubation but should not be routinely used as a tool for extubation failure.

Heterogeneity of popular boys: antisocial and prosocial configurations

This study examined subtypes of popular 4th-6th grade boys (N = 452). Popular-prosocial (model) and popular-antisocial (tough) configurations were identified by means of teacher ratings and compared with peer and self-assessments and social centrality measures. Peers perceived model boys as cool, athletic, leaders, cooperative, studious, not shy, and nonaggressive. Peers perceived tough boys as cool, athletic, and antisocial. Model boys saw themselves as nonaggressive and academically competent. Tough boys saw themselves as popular, aggressive, and physically competent. Tough boys were disproportionately African American, particularly when African Americans were a minority in their classrooms. Model and tough boys were overrepresented at nuclear social centrality levels. These findings suggest that highly aggressive boys can be among the most popular and socially connected children in elementary classrooms.

Heterogeneity of popular boys: antisocial and prosocial configurations

This study examined subtypes of popular 4th-6th grade boys (N = 452). Popular-prosocial (model) and popular-antisocial (tough) configurations were identified by means of teacher ratings and compared with peer and self-assessments and social centrality measures. Peers perceived model boys as cool, athletic, leaders, cooperative, studious, not shy, and nonaggressive. Peers perceived tough boys as cool, athletic, and antisocial. Model boys saw themselves as nonaggressive and academically competent. Tough boys saw themselves as popular, aggressive, and physically competent. Tough boys were disproportionately African American, particularly when African Americans were a minority in their classrooms. Model and tough boys were overrepresented at nuclear social centrality levels. These findings suggest that highly aggressive boys can be among the most popular and socially connected children in elementary classrooms.

Pulmonary barotrauma in congenital diaphragmatic hernia: a clinicopathological correlation

BACKGROUND/PURPOSE

The high mortality rate in congenital diaphragmatic hernia (CDH) has been ascribed to pulmonary hypoplasia and persistent pulmonary hypertension of the newborn (PPHN). One of the principal treatment strategies has been the use of hyperventilation to reverse ductal shunting, but the wisdom of this approach is being questioned because of parenchymal lung injury from high inflation pressures. The authors hypothesize that the use of hyperventilation to reverse or prevent ductal shunting would result in ventilator-induced lung injury, which would be evident on postmortem examination. A retrospective review of clinical and autopsy information was conducted.

METHODS

Clinical and autopsy information gathered for a previously published series of 223 infants with CDH presenting in the first 24 hours of life was reviewed. Autopsy and clinical data were analyzed from 68 of 101 nonsurvivors who died with severe hypoxemia.

RESULTS

Sixty-two of 68 cases (91%) had evidence of diffuse alveolar damage and hyaline membrane formation, which was more evident in the ipsilateral lung. Forty-four (65%) infants had pneumothoraces, and 4 infants had interstitial fibrosis. Pulmonary hemorrhage was seen in 35 cases (50 maximum peak inspiratory pressure [mean +/- SD] was 40.4+/-7.9 cm H2O and lowest modified ventilatory index [respiratory rate x peak airway pressure] was 2323+/-836). The degree of pulmonary hypoplasia was evaluated by lung weight with the ratio of the observed combined lung weight to the expected lung weight based on birth weight and gestational age. The ratio based on birth weight was 57%+/-25%, and the ratio based on gestational age was 60%+/-26%. Twenty-one infants (35%) had nonpulmonary anomalies. The most significant was a 10% incidence of congenital heart disease. Apart from this, lethal nonpulmonary anomalies were rare.

CONCLUSION

These results suggest that lung injury secondary to mechanical ventilation plays an important role in the mortality rate of patients with CDH, which may become increasingly significant when there is underlying pulmonary hypoplasia.

Rhabdomyosarcoma metastasizing as a malignant ectomesenchymoma

Rhabdomyosarcoma is a common childhood malignancy that may occasionally occur as a component of a mixed mesenchymal tumor, e.g., a triton tumor or malignant ectomesenchymoma. A case is reported of a 13-year-old boy who had resection of a paratesticular embryonal rhabdomyosarcoma with subsequent radiation and chemotherapy. Two years later, a retroperitoneal metastasis was resected. Histology showed a mixture of rhabdomyoblasts, ganglion cells, and a third population of cells with combined features of these two distinct cell types. Electron microscopy confirmed the presence of rhabdomyoblasts with characteristic bundles of myofilaments and Z-band material, and ganglion cells with prominent nuclei and nucleoli, rough endoplasmic reticulum, dense core granules, filaments, and tubules. Notably, the third cell population showed features of both rhabdomyoblasts and ganglion cells. Immunohistochemistry confirmed the mixed population of rhabdomyoblasts (positive for vimentin, desmin, negative for S-100, NSE), ganglion cells (positive for S-100 and NSE, negative for vimentin and desmin), and the third population expressing all test antigens. The features of this metastatic lesion are those of a malignant ectomesenchymoma with combined rhabdomyosarcoma and ganglioneuroma components. It is postulated that this lesion results from biphenotypic expression of tumor cells that previously expressed only rhabdomyoblastic differentiation. The role of prior chemotherapy and radiotherapy in this particular case is unclear.

Anorectal disease in HIV-infected patients

PURPOSE

Anorectal diseases are common in human immunodeficiency virus-infected individuals. The aim of this prospective study was to assess the cause and clinical presentation of anorectal disease in this human immunodeficiency virus-infected population.

METHODS

A registry of all human immunodeficiency virus-seropositive patients with anorectal complaints who were referred to and followed up in the colorectal surgery clinic at a county hospital was maintained, with all data collected prospectively. All patients underwent examination under anesthesia with random cultures and biopsies, along with specific sampling of any suspicious lesions.

RESULTS

Data from 180 consecutive human immunodeficiency virus-seropositive patients with anorectal symptoms were analyzed. Mean age of the population was 34 years, with a male-to-female ratio of 14:1. This group comprised homosexual and bisexual males (55 percent), injection-drug users (15 percent), heterosexuals (12 percent), and others (18 percent). The average lag time from diagnosis of human immunodeficiency virus to anorectal symptoms was 48 months. The average CD4 lymphocyte count was 160 cells/mm3. The most common symptom was anorectal pain (57 percent), followed by lumps or warts (28 percent), rectal bleeding (12 percent), discharge (11 percent), and pruritus (6 percent), with 24 percent of patients having multiple complaints. Anal condyloma was the most prevalent pathology observed (43 percent), of which 10 percent was associated with anal intraepithelial neoplasia. Wide-based anal ulcers were the most frequent noncondylomatous lesions, occurring in 32 percent of patients, with the majority (91 percent) presenting with the chief complaint of anorectal pain. Some of these ulcers were associated with viral infections: herpes simplex virus (12 percent) and cytomegalovirus (7 percent). However, most ulcers were idiopathic, with negative cultures and biopsies. Other lesions encountered included fistulas (14 percent), abscesses (12 percent), hemorrhoids (6 percent), and malignancy, with two cases of Kaposi's sarcoma, one case of non-Hodgkin's lymphoma, and one case of squamous-cell carcinoma. More than one anorectal condition was identified in 16 percent of the patients.

CONCLUSIONS

Human immunodeficiency virus infection is associated with a wide spectrum of anorectal disease, of which the most common lesions are anal condylomata and painful ulcers. The majority of these anal ulcers gave negative culture and biopsy results. In addition, there seems to be a high incidence of anorectal neoplasia in this patient population.

Multidisciplinary evaluation of the distended abdomen in critically ill infants and children: the role of bedside sonography

Abdominal distention and metabolic acidosis are common in critically ill infants and children, and can be manifestations of an intra-abdominal catastrophe. This series demonstrates the value of bedside sonography (US) in this difficult assessment. Eight infants and children presented with the above situation. Seven were immediately post-cardiopulmonary resuscitation and none had antecedent histories of abdominal pain or bilious vomiting. Abdominal radiographs could not rule out intra-abdominal pathology such as ischemic bowel. Review of all laboratory and radiological data showed US to be a discerning modality for acute bowel pathology. A characteristic pattern of echogenic ascites, thickened bowel wall, dilated, fluid-filled bowel lumen, and lack of peristalsis was seen in those children with gangrenous bowel. Sonographic examination accurately predicted the status of the bowel in all patients. Four patients survived: two had segmental ileal necrosis, one had localized gangrene of the jejunum (twice), and one had necrotic bowel from a closed-loop obstruction. The four who died had malrotation with volvulus (two), superior mesenteric venous thrombosis, and one was immunocompromised with pulmonary aspiration. We conclude that bedside US can be extremely valuable as an adjunct in assessing the abdomen and diagnosing gangrenous bowel in critically ill infants and children.

Congenital diaphragmatic hernia--a tale of two cities: the Toronto experience

PURPOSE

The optimal therapy for congenital diaphragmatic hernia (CDH) is evolving. This study analyzes the results of treatment of CDH in a large tertiary care pediatric center using conventional and high-frequency oscillatory ventilation (HFOV) without extracorporeal membrane oxygenation (ECMO) contrasting these with a parallel study from a similar large urban center using conventional ventilation with ECMO.

METHODS

Between 1981 and 1994, 223 consecutive neonates who had CDH diagnosed in the first 12 hours of life were referred for treatment before repair. Conventional ventilation was used with conversion to HFOV for refractory hypoxemia or hypercapnia, and a predicted near 100% mortality rate. ECMO was used in only three patients, all of whom died. A retrospective database was collected. Thirty-one clinical variables were tested for their association with the outcome. Common ventilatory and oxygenation indices were tested for their prognostic capability.

RESULTS

Apgar scores, birth weight, right-sided defects, pneumothorax, total ventilatory time, and the use of high frequency oscillatory ventilation were the only variables associated with outcome. A modified ventilatory index and postductal A-aDo2 were strong prognostic indicators. From 1981 to 1984 surgery was performed on an emergency basis. Since 1985 surgery was deferred until stabilization had been achieved. This resulted in a shift in the mortality from postoperative to preoperative with no change in total survival. HFOV did not alter the overall survival. Results of autopsies performed (70%) showed significant pulmonary hypoplasia and barotrauma as the primary causes of death. The survival was 54.7%.

CONCLUSION

Conventional ventilation with HFOV produced equal survival to conventional ventilation with ECMO in two comparable series. Pulmonary hypoplasia was the principle cause of death. This continued high mortality at both centers suggests that new therapies are required to improve outcomes.

Using genetic information to make surgical decisions: report of a case of a 13-year-old boy with colon cancer

PURPOSE

We report the case of a boy aged 13 years who was diagnosed with a Dukes B obstructing cancer of the sigmoid colon. At the time of diagnosis, he underwent a Hartmann's procedure with end colostomy. Because of his unusually young age, he was referred to the Familial GI Cancer Registry at Mount Sinai Hospital for genetic assessment. A detailed pedigree revealed no significant history other than lung cancer in his maternal grandfather.

METHODS

We obtained his tumor specimen and performed molecular analysis of both normal colonic and tumor DNA. Specifically, we identified replication errors (RER) in the patient's tumor DNA when compared with normal colonic DNA. RER has been found in more than 90 percent of tumors from patients with Hereditary Nonpolyposis Colon Cancer (HNPCC) and is, thus, considered to be one of the hallmarks of this disease. Because HNPCC patients have a 40 percent risk of synchronous or metachronous tumors, the recommended surgery for HNPCC should be at least a subtotal colectomy with ileorectal anastomosis.

RESULTS

Based on molecular results, we were able to recommend that the patient have a subtotal colectomy performed instead of merely colostomy closure, to reduce his lifetime risk of developing further colon tumors and to make surveillance of the remaining rectum relatively easy. In this patient, we subsequently identified a germline mutation of the mismatch repair gene hMSH2 that is implicated in HNPCC. The possibility of HNPCC should be considered in adolescents who are diagnosed with colorectal cancer, so appropriate surgical decisions can be made.

Postnatal management of congenital diaphragmatic hernia

The emphasis in postnatal management has shifted from the neonatal surgical emergency approach to strategies designed to deal with pulmonary hypoplasia and the pulmonary vascular abnormalities. There has been extensive experience with alternative ventilation strategies such as ECMO and high frequency ventilation, without there being convincing evidence that these have had a major impact on mortality. Strategies that emphasize the importance of minimizing ongoing lung injury, such as pressure limited (permissive hypercapnia) ventilation and the use of surfactant replacement therapy, are beginning to show some encouraging results.

Imaging gastrointestinal perforation in pediatric blunt abdominal trauma

OBJECTIVE

To assess the role of imaging, in particular CT, in the early detection of GI perforation.

SUBJECTS AND METHODS

In a 10-year period, 43 patients with surgically confirmed GI perforation were identified from hospital records; 22 of these had preoperative CT evaluation. Medical records and radiology were retrospectively reviewed and CT studies were particularly assessed for extraluminal air, free intraperitoneal fluid, bowel wall thickening, bowel wall enhancement, and bowel dilatation. During the study period an additional 12 trauma patients were identified who had CT studies demonstrating the above findings, but who had hypovolemic shock bowel or nondisrupting bowel injury without perforation evident.

RESULTS

Extraluminal air was demonstrated in 47 % of the imaged perforations. There was one false-positive extraluminal air. Perforation was confirmed in patients who had all five of the above CT findings, but this was the case for only 18 % of patients with perforation. One or more of the five specified CT findings were present in all CT studies reviewed. No false-negative CT study was performed in the study period.

CONCLUSION

Separating nondisrupting bowel injury from perforation is diagnostically difficult; however, CT remains a good modality for assessing GI perforation in pediatric blunt trauma, but it cannot replace diligent and repeated clinical evaluation of all potential perforation victims.

Antibody facilitation of multiple sclerosis-like lesions in a nonhuman primate

In the human disease multiple sclerosis (MS), the immune mechanisms responsible for selective destruction of central nervous system myelin are unknown. In the common marmoset Callithrix jacchus, a unique demyelinating form of experimental allergic encephalomyelitis resembling MS can be induced by immunization with whole myelin. Here we show that the MS-like lesion can be reproduced by immunization against the extracellular domain of a single myelin protein, myelin/oligodendrocyte glycoprotein (MOG). By contrast, immunization against the quantitatively major myelin proteins myelin basic protein or proteolipid protein results in inflammation but little or no demyelination. Furthermore, in the presence of encephalitogenic (e.g., disease-inducing) T cells, the fully demyelinated lesion is reconstructed by systemic administration of IgG purified from whole myelin-, or MOG-immunized animals, and equally by a monoclonal antibody against MOG, but not by control IgG. Encephalitogenic T cells may contribute to the MS-like lesion through disruption of the blood-brain barrier that permits access of demyelinating antibody into the nervous system. The identification of MOG as a major target antigen for autoimmune demyelination in a nonhuman primate should facilitate development of specific immunotherapies for human MS.

Conversational interactions of mothers and their preschool children who had been born preterm

This study examined the conversational interactions of mothers and their 4.5-year-old children, who had been born preterm, during a social problem-solving task asking each dyad to agree on the choice of a snack. Relative to comparison mothers, mothers of preterm children seemed to approach the task as a vocabulary lesson; they produced less complex sentences and were more likely to name the snacks and to test their children's knowledge of snack names. Comparison mothers were more likely to focus on the social negotiation aspect of the task, by offering more opinions and reasons. Discussed is whether the conversational strategies of mothers of preterm children reflect appropriate "fine-tuning" or a lag in adjusting to their children's emerging language skills because of a lingering "prematurity stereotype."

Brief report: four years after a preterm birth: children's development and their mothers' beliefs and expectations

Examined the development of preterm-born 4 1/2-year-olds who lived in environments free from socioeconomic disadvantages often associated with deleterious outcomes. Beliefs and expectations of their mothers were also assessed. Thirty-two preterm and 41 comparison children and their mothers participated. Results indicated that although the preterm children were performing at or above age norms on most measures, they scored lower than comparison children in receptive vocabulary, syntactic complexity, articulation, and visual-motor skill. In addition, preterm and comparison group mothers differed in some beliefs and expectations. Results suggest that a preterm birth remains a factor in development during the preschool period, even in a social environment most likely to provide compensatory mechanisms for preterm birth.

Getting caught in misconduct: conceptions of adolescents with and without learning disabilities

This study examined adolescents' conceptions about how to respond after being caught in misconduct, in order to determine whether students with learning disabilities differ from nondisabled students in their beliefs regarding apprehension. A total of 88 students with learning disabilities (62 male, 26 female) and 84 nondisabled students (45 male, 39 female) were interviewed about 10 scenarios in which a teenager was caught by authorities after participating in misconduct, either alone or with a peer. The mean age of the students was 16 years (SD = 1.4). The results indicated that the students with learning disabilities were significantly more likely than other students to suggest escaping and less likely to suggest accepting the consequences, although the differences were not great. The implications of these findings are discussed.

Efficacy of immobilization following aspiration of carpal and digital ganglions

In a prospective study 69 carpal and digital ganglions were aspirated, multiply punctured, and digitally ruptured. Fifty percent of the wrists and digits were immobilized for 3 weeks and 50% were mobilized early. Follow-up was 1 year. Immobilization in our study did not significantly improve the results of treatment. During the course of the study, 51% of all ganglions did not recur. The outcome was successful in 52% of the wrists and digits that were immobilized and in 50% of those that were not. Forty-six percent of the dorsal carpal ganglions did not recur. Treatment was successful in 48% of dorsal carpal ganglions in which the wrists were immobilized and in 45% of those that were not. Similar percentages were found for palmar and digital ganglions. From our results, we conclude that immobilization does not significantly improve the successful treatment of ganglions over perforation and aspiration alone.

The management of vascular injuries associated with total hip arthroplasty

Approximately 100,000 total hip reconstructions are done annually in the United States. The nature of the surgical technique in a field close to the iliac and femoral vessels makes the occurrence of vascular injury an occasional but serious complications. We have reviewed retrospectively our experience of five cases of vascular injuries with total hip replacement and an additional 63 cases in the literature to identify those patients at risk and to define the management of these injuries. For the entire group of 68 patients, most injuries were sustained on the left side (66%), and 39% were seen in revisions. Complications were related to cement incorporation of the iliac vessels (44%), aggressive medial retraction (17%), excessive traction on atherosclerotic vessels (10%), and improper technique in preparation of the acetabulum. The most commonly injured vessels were the external iliac artery (36), common femoral artery (17), and external iliac vein (6). Twenty-seven of these injuries required emergent surgery, most for hemorrhage (66%). Injuries consisted of thromboembolic complications leading to distal ischemia (46%), vessel lacerations (26%), pseudoaneurysms (25%), and arteriovenous fistulas (3%). Vascular repair was individualized and included suture repair, thrombectomy and patch angioplasty, embolectomy, and arterial and venous bypass procedures. There was an overall 7% mortality and a 15% incidence of limb loss. Risk factors include (1) revision procedures, (2) left-sided procedures, and (3) intrapelvic migration of the acetabular component of the hip prosthesis. Elective vascular workup and preliminary retroperitoneal exposure of the iliac vessels at time of hip arthroplasty is recommended for patients at risk.

Cognitive-behavioral interventions for increasing motivation

Interventions aimed at improving students' achievement behavior by promoting adaptive attributions for success and failure are described. Issues concerning identification of appropriate recipients of these interventions, content and method of training, and evaluation of treatment effectiveness are discussed.

Amino acid clearance and prognosis in surgical patients with cirrhosis

To measure the effects of cirrhosis on amino acid (AA) flux and to assess the value of the central plasma clearance rate of amino acids (CPCR-AA) as a hepatocyte function test, 35 patients with cirrhosis were studied before and after operation. Fourteen of these patients died after the operation. CPCR-AA measures the number of milliliters of plasma cleared of AA per minute by the liver and other visceral tissues. It is the ratio of AA entry rate into plasma (from peripheral tissues plus infusion) to the arterial AA plasma concentration. Preoperative CPCR-AA measurements in 21 fasted patients with cirrhosis who were not infected revealed a pattern of AA plasma concentration and exchange similar to that previously observed in patients with sepsis with normal liver function. Whereas the concentration of AA in both groups was slightly lower than normal, the CPCR-AA of each was more than four times that of normal postabsorptive people (p less than 0.01). However, preoperative values of CPCR-AA in patients with cirrhosis who survived was 220 +/- 26 ml/M2/min while that in those who died was 97 +/- 16 ml/M2/min (p less than 0.001). Postoperative measurements remained relatively unchanged: survivors 212 +/- 24 ml/M2/min and those who died 89 ml/M2/min (p less than 0.0005). Measurements in vitro of the hepatic protein synthetic rate in liver biopsy specimens taken at operation correlated well with CPCR-AA values obtained immediately before operation in 10 patients (r = 0.73; p less than 0.01). Thus in patients with cirrhosis visceral amino acid uptake and hepatic protein synthesis are maximally stimulated. Nevertheless, if the preoperative CPCR-AA does not approach the value of 284 +/- 76 ml/M2/min previously observed in patients with sepsis who recover, the patient with cirrhosis is prone postoperatively to die of overwhelming infection and multisystem failure.

Conversational interactions between mothers and learning-disabled or nondisabled children during a problem-solving task

This study focused on mother-child interactions during a problem-solving task to determine whether (a) mothers of learning-disabled children engage in conversational buffering to facilitate their child's participation in the task, and (b) whether learning-disabled children differ from nondisabled children in their use of language with their mothers. The results of this study provide some evidence that mothers of both learning-disabled and nondisabled children engage in conversational buffering, although there were few differences between the mothers of the learning-disabled and nondisabled children. Differences between learning-disabled and nondisabled children showed that the learning-disabled were more likely to agree with and less likely to disagree with their mothers than were the nondisabled children. These findings provide some evidence of maternal conversational buffering and suggest that learning-disabled children's previously reported unassertive conversational style in peer interactions extends to talk with their mothers.

Learning disabled children's syntactic proficiency on a communicative task

Previous studies have generally examined learning disabled children's syntactic ability either on structured tasks or by analyzing oral language samples collected under conditions not typical of natural communicative settings. Thus, these studies are of limited value in exploring the impact of learning disabled children's deficits in linguistic structure on their use of language in social contexts. The purpose of this study was to investigate learning disabled children's syntactic proficiency during a task requiring them to convey information to a listener. Subjects were selected on the bases of teacher ratings, reading achievement scores, and Peabody Picture Vocabulary Test IQ scores within the normal range; those children identified as learning disabled received low ratings and demonstrated underachievement (below 40th percentile for their grade) in reading. Oral language samples were collected by having learning disabled and normally achieving children in grades two, four, six, and eight participate in a referential communication task in which they described abstract shapes to an experimenter. The length and syntactic complexity of the children's descriptions were assessed. Learning disabled children in all grades were found to produce shorter mean t-units and shorter mean main clauses than nondisabled children even on this relatively simple communicative task. Although learning disabled children's linguistic problems have previously been characterized as subtle, these findings suggest that their productive language deficits may be significant enough to interfere with even the informal and elliptical conversations characteristic of communication among peers and family members.

The classification of acute leukaemia in childhood

In 1976 a French, American and British (FAB) cooperative group proposed a morphological classification of acute leukaemia which they hoped would prove more reproducible than previous classification. We present our preliminary experience with this classification, based on a 2-year study of 39 patients. Cytochemical and cell surface marker characteristics of the leukaemic cells were also studied. We found this classification to be satisfactory but some problems were noted in regard to its reproducibility, especially in acute lymphoblastic leukaemia (ALL). Cell surface markers were absent in the majority of cases of ALL ("null cell" type), while the remainder had T-cell characteristics. No B-cell types were seen. Cytochemical staining patterns clearly distinguished ALL from acute myeloid leukaemia (AML) and also helped to categorize AML into its subtypes. The implications of our finding are discussed.

THE GROWTH AND DURATION OF LIFE OF CELOSIA CRISTATA SEEDLINGS AT DIFFERENT TEMPERATURES

Daily measurements of hypocotyl length were made on Celosia cristata seedlings cultured in darkness under aseptic conditions at six constant temperatures between 14.5° and 40.5°C. At 40.5° roots did not penetrate the agar and only the hypocotyls that were supported by the wall of the test tube could be measured. The growth curves were of the generalized logistic type, but of different degrees of skewness. The degree of symmetry of the growth curves was influenced by temperature. At the lower temperatures the maximal growth rate came relatively late in the grand period of growth; at successively higher temperatures it came progressively earlier. The mean total time rate of growth (millimeter per diem) was found to be a parabolic function of the temperature. The maximum rate of growth was found from the curve to be at 30.48°C. The maximum observed rate of growth, and the maximum yield, were found to be at 30°C. At all temperatures above 14.5° the maximum growth activity fell in the second quarter of the whole growth period. At all temperatures tested other than 30°, and at all parts of the growth cycle, the growth yield as measured by height of hypocotyl at any given equivalent point was less than at 30°. The total duration of life of the seedlings, and the duration of life after the end of the growth period (intermediate period) were inversely proportional to the mean total growth rate. The observations on Celosia cristata seedlings are thus in accord with the "rate of living" theory of life duration. The optimal temperature for life duration is the minimum temperature, within the range of these observations.