Morphological differentiation and nitrogen fixation in transposon generated mutants of Anabaena 7120

Mutants having partially repressed glutamine sythetase (transferase) activity and high nitrogenase activity were isolated following transposon mutagenesis. Two of these mutants M11 and M73 showed a decrease in heterocyst frequency compared with the wild type strain. The level of the enzyme nitrogenase was much higher in all the mutant strains. Nitrate and ammonia completely suppressed heterocyst differentiation and nitrogenase activity in mutants M11 and M73, but mutant M55 differentiated heterocysts and showed nitrogenase activity even in the presence of these combined inorganic nitrogen sources. Heterocyst frequency in the M55 mutant was much more than that of the wild strain. Glutamine as a nitrogen source completely suppressed differentiation of heterocysts as well as nitrogenase activity, irrespective of the presence or absence of the glutamate analogue MSX which relieved the inhibitory effect of nitrate or ammonia on heterocyst differentiation and nitrogenase activity. The level of the intracellular ammonium pool was maximal in the wild strain in all the nitrogen sources used for growth. Cultures raised with ammonium chloride gave maximum values for intracellular ammonium pool in all the mutant strains and the wild strain. Mutants showed about 55 to 60% less GS (transferase) activity than the wild strain.     

Regional audit of pedestrian accident care

In all, 160 serious pedestrian accidents (ISS > 15 or death), were recorded during a 12-month prospective study of all trauma in a population of 3.2 million. Of these, 35 died at scene, 125 arrived at hospital alive and 68 (54 per cent) subsequently died. There were 35 (22 per cent) children, and 62 per cent (39) were more than 60 years of age. Prehospital care significantly delayed transfer to hospital. In the accident and emergency department, only 38 per cent of those unconscious had a cervical collar applied, and only 67 per cent were intubated. Of those transferred for neurosurgical care, 34 per cent were not intubated. The Median Injury Severity Score for each outcome group was similar between age groups. The Revised Trauma Score and APACHE II score showed significant differences between those who lived and died. TRISS analysis revealed that 32 per cent of deaths and 12 per cent of survivors were unexpected. ATLS treatment protocols should be instituted for prehospital care and in all accident and emergency departments (A&E).     

Intrapleural placement of a nasogastric tube: an unusual complication of nasotracheal intubation

PURPOSE: Although rare, the misplacement of nasogastric tubes into the pleural space has been described. The prognosis of such injuries is improved by prompt recognition; therefore, it is important for physicians who practice nasogastric intubation to be aware of this potential complication, and to be familiar with an approach to early diagnosis. CLINICAL FEATURES: We present a case of perforation of the cervical oesophagus by a polyvinylchloride nasogastric tube, following a traumatic attempt at nasotracheal intubation. This resulted in passage of the nasogastric tube into the pleural space. CONCLUSIONS: Our experience with this case and a review of the relevant literature suggest that such trauma may predispose to malplacement of nasogastric tubes. Clinical signs, such as aspiration of fluid from a nasogastric tube, and auscultation of air insufflated into the stomach, are unreliable; however, the presence of subcutaneous air in the neck on chest radiograph, and the presence of cervical crepitance on physical examination, are valuable signs in the early diagnosis of perforation of the cervical oesophagus. Contrast oesophagography remains the diagnostic manoeuvre of choice in confirming the diagnosis, but early diagnosis will depend on a high index of suspicion and prompt viewing of chest x-rays. The management and the prognosis of such injuries depends on the level of the perforation, delays in diagnosis, and the presence of associated mediastinitis.     

Compound heterozygous protein C deficiency resulting in the presence of only the beta-form of protein C in plasma

About 30% of human plasma protein C (PC) is of lower molecular weight than the predominant alpha-form. The minor beta-form arises as a consequence of the lack of glycosylation at Asn329. Although the functional role of Asn329 has been investigated by in vitro mutagenesis, until now no naturally occurring mutations have been reported at this site. We describe here the case of two identical twin sisters compound heterozygous for two novel PC mutations: Cys78-->Stop inherited from the maternal side and Asn329-->Thr inherited from the paternal side, associated with the presence of only the beta-form of PC in plasma. The Cys78-->Stop substitution is predicted to abolish PC synthesis from one allele, whereas the Asn329-->Thr substitution results in the reduced synthesis of a beta PC variant with decreased functional activity. PCN329T from the two monovular twin sisters was purified and its active form APCN329T was assessed for its ability to inactivate factor Va. Whereas no differences were observed between the activation rates of normal PC and PCN329T, APCN329T inactivated human factor Va with a rate slower than the normal APC. This is the first report of a PC defect involving glycosylation of the molecule. This defect results in the presence of only the beta-form of PC in human plasma and is responsible for the reduced anticoagulant activity observed.     

The biosynthesis of human hemoglobin A1c. Slow glycosylation of hemoglobin in vivo

Hemoglobin A1c, the most abundant minor hemoglobin component in human erythrocytes, is formed by the condensation of glucose with the N-terminal amino groups of the beta-chains of Hb A. The biosynthesis of this glycosylated hemoglobin was studied in vitro by incubating suspensions of reticulocytes and bone marrow cells with [3H]leucine or 59Fe-bound transferrin. In all experiments, the specific activity of Hb A1c was significantly lower than that of Hb A, suggesting that the formation of Hb A1c is a posttranslational modification. The formation of Hb A1c in vivo was determined in two individuals who were given an infusion of 59Fe-labeled transferrin. As expected, the specific activity of Hb A rose promptly to a maximum during the 1st week and remained nearly constant thereafter. In contrast, the specific activity of Hb A1c and also of Hbs A1a and A1b rose slowly, reaching that of Hb A by about day 60. These results indicate that Hb A1c is slowly formed during the 120-day life-span of the erythrocyte, probably by a nonenzymatic process. Patients with shortened erythrocyte life-span due to hemolysis had markedly decreased levels of Hb A1c.     

Clinical and radiographic diagnosis of occlusal caries: a study in vitro

We report on the autopsy study of a premature boy with multiple joint contractures who died soon after birth of severe lung hypoplasia. Muscle histology showed PAS-positive vacuoles, and electronmicroscopy revealed massive subsarcolemmal and intermyofibrillar accumulation of glycogen. Biochemical analysis of fresh-frozen muscle tissue disclosed increased glycogen content and a complete lack of phosphofructokinase (PFK) activity. The brain showed focal cerebral and diffuse cerebellar white matter gliosis, and patchy loss of internal granular and Purkinje cells in the cerebellar cortex. The spinal cord was normal. This report describes the first case of PFK deficiency, presenting as a lethal fetal akinesia sequence.     

Effects of gravity on tracheal mucus transport rates in normal subjects and in patients with cystic fibrosis

A noninvasive, radionuclide imaging technique for measuring the rate of mucus clearance in the trachea (RT), was used to study gravitational effects on mucus clearance in 13 patients with cystic fibrosis (CF), average age 17 years; 7 normal, nonsmoking adults, average age 26 years; and a normal subject who was recovering from an acute upper respiratory tract infection (URTI). In the upright position, nine of the CF patients and the subject with URTI demonstrated abnormal tracheal mucus clearance which approached normal when they were placed in 25 degrees headdown position. The normal subjects and two of the CF patients showed no significant difference in the RT measured in the two positions. The results of the study indicate that the force of gravity can be a major influence on tracheal mucus clearance in CF and URTI subjects. This conclusion supports the use of postural drainage as an effective form of therapy in patients with cystic fibrosis.     

Role of the kidney in regulating plasma immunoreactive beta-melanocyte-stimulating hormone

An analysis of the factors that influence the increase in plasma immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) concentration in chronic renal failure showed that: (a) the increase correlated with the increase in serum creatinine concentrations; (b) beta-MSH was not cleared from the plasma by haemodialysis; (c) beta-MSH concentrations increased with length of time on dialysis and increased further after bilateral nephrectomy but there was no further increase with time; (d) beta-MSH levels decreased to normal after renal transplantation; and (e) beta-MSH was excreted in urine only when plasma levels rose to well above those of chronic renal failure (in Nelson's syndrome). These findings suggest that the kidney regulated plasma beta-MSH by a non-excretory mechanism and is the major site of beta-MSH metabolism.