Pneumococcal carriage amongst children in Adelaide, South Australia

Amongst 1267 healthy children 6 months to 4.5 years of age in Adelaide, the pneumococcal carriage rate from a single nasal swab sampling was 29% in the period 1980-1. Of 269 children, sampled monthly on five occasions, 91% carried a pneumococcus on one or more occasions: 55% carried a single type, 33% carried two types, 2% carried three types and 1% carried four types; 18% carried a pneumococcus on either 4 or 5 occasions. The commonest types encountered were types 6, 19 and 23 in that order, and these three types constituted 57% of the total: other common types (greater than 5% of the total) were types 14, 15 and 11, and the six commonest types constituted 77% of the total. Of these, types 6, 14, 19 and 23 commonly cause systemic disease in children; on the other hand types 11 and 15 cause disease infrequently. The number of strains showing antimicrobial drug resistance was low: on quantitative testing 0.7% of 291 isolates examined showed relative resistance to benzylpenicillin and 0.7% were resistant to tetracycline; 10.9% of 230 isolates examined showed resistance to co-trimoxazole; dual or multiple drug resistance was not detected, and all isolates tested were susceptible to chloramphenicol, erythromycin, lincomycin and rifampicin.

Tree LANs with collision avoidance: protocol, switch architecture, and simulated performance

Packet collisions and their resolution create a performance bottleneck in random access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the implementation of random access protocols without the penalty of collisions among packets. We describe the designs of some tree LANs that use collision avoidance switches. The collision avoidance LANs we describe are broadcast star and CAMB tree (Collision Avoidance Multiple Broadcast tree). We next present a possible implementation of a collision avoidance switch using currently available photonic devices. Finally, we show the performance of broadcast star and CAMB tree networks using simulations.

The effects of nasal anaesthesia upon nasal sensation of airflow

The effect of nasal anaesthesia upon the sensation of nasal airflow and activity of menthol was investigated in 25 subjects using a visual analogue scale. Nasal anaesthesia was shown to decrease the sensation of nasal airflow, and also decrease the action of menthol in enhancing the sensation of nasal airflow. These differences were shown to be highly significant p less than 0.001. Physiological mechanisms responsible for conveying the subjective appreciation of a nasal airflow stimulus are discussed, and also the site and nature of the sensory nerve endings involved.

Age-dependent variation for inducibility of metallothionein genes in mouse liver by cadmium

Cadmium is a toxic metal that induces the expression of metallothionein genes in many tissues and that binds avidly to metallothionein, a soluble transition metal binding protein. The present study examined the temporal pattern and magnitude of accumulation of metallothionein mRNA in liver of C57BL/6J mice of various ages treated with cadmium. In adult female mice, accumulation was dependent on the dosage level of cadmium and related to the concentration of this metal in liver. The accumulation of metallothionein mRNA in liver depended on age at exposure to cadmium. Intraperitoneal administration of 2 mg of cadmium per kg provoked small increases (two- to threefold) in levels of metallothionein mRNA in livers of 7- and 14-day-old mice. In contrast, cadmium treatment of 28- and 56-day-old mice resulted in 12- to 19-fold increases in levels of metallothionein mRNA in liver with maximum increases occurring 3 to 4 hr after treatment. Because similar patterns for the accumulation of cadmium of liver were found in 7-, 28-, and 56-day-old mice, observed age-dependent differences in induction of metallothionein mRNA in liver were probably not due to differences in the accumulation of cadmium in this organ. Taken together, these data suggest that tissue-specific factors controlling the expression of metallothionein genes may account for developmental variation in the inducibility of these genes by cadmium. Ontogenic variation in accumulation of metallothionein mRNA after cadmium treatment may be a factor in developmental variation in the acute lethality of cadmium in C57BL/6J mice.

Disruption of follicular maturation and delay of ovulation after administration of the antiprogesterone RU486

To investigate the role of progesterone in the follicular phase, we examined the effects of RU486 in eight normal cycling women studied with daily and frequent blood sampling (every 10 min for 10 h) during three menstrual cycles (control-treatment-recovery). RU486 (3 mg/kg, orally) was administered for 3 consecutive days after ultrasound documentation of a dominant follicle. In six of the eight women, RU486 was given after emergence of the dominant follicle, while in two women, RU486 was initiated during the preovulatory period when estradiol levels had exceeded 917 pmol/L. In the six women given RU486 after emergence of the dominant follicle, RU486 significantly prolonged the follicular phase duration from 15.6 +/- 1.9 (+/- SD) to 28.6 +/- 9.3 days (P less than 0.01) and extended the treatment cycle length to 42.3 +/- 9.1 (+/- SD) days (P less than 0.01). During RU486 treatment, mean serum estradiol levels decreased from 385 +/- 43 to 228 +/- 28 pmol/L (P less than 0.01), while LH, FSH, ACTH, cortisol, and progesterone levels changed little. LH pulse frequency and amplitude on the last day of RU486 administration did not differ from control values. Collapse of the dominant follicle was evident on ultrasound after RU486 administration and was not accompanied by uterine bleeding. In the two women treated during the preovulatory period, the follicular phase was not prolonged, and RU486 failed to delay the onset of the LH surge. Our findings indicate that RU486 treatment during the follicular phase interrupts normal follicular development, resulting in a delay of ovulation and a reinitiation of follicular recruitment.

A randomised comparison of three drainage systems following cholecystectomy

The efficacy of low pressure, high pressure and passive drainage systems have been compared after cholecystectomy. Symptoms of pain, discomfort and nausea were compared using linear analogue scales and spirometry was used to examine pre-operative and postoperative respiratory function. The low pressure suction drain removed an intraperitoneal marker, gentamicin, more effectively than the high pressure suction drain, but not more effectively than the passive drain. There were no differences in postoperative respiratory function nor in the amount of pain or discomfort between the groups. The passive drain group reported less nausea than the suction drain groups. If a negative pressure drainage system is to be used, a low pressure suction drain should be used in preference to a high pressure system.

Bronchial anastomosis with a tissue adhesive

Air leakage and necrotic degeneration may occur after bronchial anastomosis and can lead to death from secondary pneumothorax and pneumonia. We studied the ability of a new tissue adhesive (N-butyl-cyanoacrylate monomer) to enforce the bronchial suture line. The left main bronchus in each of five pigs in Group A was completely transected and closed by four stitches and tissue adhesive. The transected left main bronchus in each of the other five pigs in Group B was connected with 11 to 14 interrupted polyglycolic acid 3-0 sutures. The time required for reconstruction was 10 +/- 3.6 minutes in Group A and 25.0 +/- 6.5 minutes in Group B. No symptoms of a constricted airway were apparent in Group A. All pigs were examined at an interval of from 5 to 8 weeks after operation. Evidence of infection at the bronchus appeared in three animals: two in Group A and one in Group B. One instance of air leakage at the anastomosis occurred in Group B. We measured the maximum tensile strength of the bronchial suture line by means of an electromechanical testing machine comparing the tensile strength of the treated left bronchus with that of the control right bronchus. The maximum tension of the treated bronchus in Group A was 10.3 +/- 1.52 (pounds) and that of control was 8.0 +/- 1.56 (pounds) (p less than 0.05). The maximum tension of Group B was 7.93 +/- 0.29 (pounds) on the treated side and 6.78 +/- 0.32 (pounds) on the control side (p less than 0.05). The suture line with tissue adhesive was enforced sufficiently to act as a stable connective tissue. Histologic studies in Group A revealed that the suture line was completely healed without tissue damage and was strengthened by the tissue adhesive.

Transient response of amplified metallothionein genes in CHO cells to induction by alpha interferon

Alpha interferon treatment of CHO cells elicits the rapid synthesis of many gene products, including metallothionein (MT), a protein which avidly binds heavy metals such as zinc, cadmium, and copper. Since MTs appear to have a pleiotropic role in the cell, ranging from metal detoxification to free-radical scavenging, interferon treatment may trigger a generalized defense mechanism. Activation by interferon, however, was transient, with MT mRNA being maximally detectable by a cytodot procedure within the first hour. Subsequent addition of interferon was ineffective until 7 h after the initial treatment. The action of zinc, a potent inducer of MT, however, remained independent of alpha interferon induction. The transient nature of induction by interferon was examined for altered rate of MT mRNA turnover.

Role of metallothionein in detoxification and tolerance to transition metals

Animal tolerance to the transition metals cadmium and zinc is hereditary. The evolution to a high level of resistance can be accelerated through mutation and selective pressure. We have studied inbred strains of mice and mutants of Chinese hamster ovary cells resistant to cadmium to further these understandings. Results with whole animals show that the difference in the rate and level of metallothionein accumulation is at most twofold between sensitive and resistant strains. However, with cadmium resistant CHO mutant cells, there is an over 60 fold increase in metallothionein and its mRNA upon induction. These mutants show over 60 fold amplification in metallothionein genes. These results offer a direct contrast in the correlation between elevation of metal resistance and increases in metallothionein between two genetic systems.

Pneumococcal carriage amongst Australian aborigines in Alice Springs, Northern Territory

In Alice Springs and its vicinity, a single nasal swab was collected from 282 Australian aborigines in May 1981 to determine nasal carriage rates of pneumococci. Each swab was inoculated on blood agar and on gentamicin blood agar. The carriage rates were 89% in children, 39% in adolescents and 34% in adults. In all, 27 serotypes of pneumococci were met with and 15 (4%) of subjects yielded two or more serotypes. In children, types 23, 19, 6, 22 and 6 were predominant (in that order), whereas type 3 was commonest in older subjects. Approximately 25% children and 5% adults yielded drug-insensitive pneumococci. Resistance to benzylpenicillin, tetracycline and co-trimoxazole was met with, resistant pneumococci showed five resistance patterns and belonged to nine serotypes, predominantly types 19 and 23. All isolates were sensitive to chloramphenicol, erythromycin, lincomycin and rifampicin. The carriage rate of drug-insensitive pneumococci was 100-fold higher amongst children sampled than in non-aboriginal children in Australia.

Exercise-induced left bundle branch block and its relation to coronary artery disease

The records of 2,584 consecutive patients who underwent both treadmill exercise testing and coronary cineangiography were reviewed to determine the relation between exercise-induced, acceleration-dependent left bundle branch block (LBBB) and the presence of coronary artery disease (CAD). Rate-dependent LBBB during exercise was identified in 28 patients (1.1%), who were categorized according to their presenting symptoms: classic angina pectoris, atypical chest pain, symptomatic cardiac arrhythmia and asymptomatic. Asymptomatic patients underwent a screening exercise test. CAD was present in 7 of 10 patients who presented with classic angina pectoris, but 12 of 13 patients presenting with atypical chest pain had normal coronary arteries. All 10 patients in whom LBBB developed at a heart rate of 125 beats/min or higher were free of CAD, whereas 9 of 18 patients in whom LBBB developed at a heart rate of less than 125 beats/min had CAD. Normal coronary arteries were present in 3 patients who presented with angina and in whom both chest pain and LBBB developed during exercise. It is concluded that patients who present with atypical chest pain in whom rate-dependent LBBB develops on the treadmill are significantly less likely to have CAD than patients who present with classic angina; the onset of LBBB at a heart rate of 125 beats/min or higher is highly correlated with the presence of normal coronary arteries, regardless of patient presentation; and patients with angina in whom both chest pain and LBBB develop during exercise may have normal coronary arteries.

Cellular heterogeneity in the expression of the delta-crystallin gene in non-lens tissue

RNA transcripts of the delta-crystallin genes, which code for the major chicken lens protein, have been detected at low levels in many non-lens tissues. Here it is demonstrated by in situ hybridisation that these transcripts are concentrated at a high level in small, infrequent clusters of cells in many non-lens tissues. While the nuclei of these cells are very heavily labelled, there is only light labelling of the cytoplasm. The unlabelled cells surrounding the labelled clusters are of similar morphology and staining properties as the labelled cells, and all have the characteristic morphology of cells of the embryonic tissue used. With the exception of neural retina, it is not yet known whether the labelled clusters are found in specific locations in the tissues, or whether they arise at random.