A Unifying Framework for Understanding Biological Structures and Functions Across Levels of Biological Organization.

The relationship between structure and function is a major constituent of the rules of life. Structures and functions occur across all levels of biological organization. Current efforts to integrate conceptual frameworks and approaches to address new and old questions promise to allow a more holistic and robust understanding of how different biological functions are achieved across levels of biological organization. Here, we provide unifying and generalizable definitions of both structure and function that can be applied across all levels of biological organization. However, we find differences in the nature of structures at the organismal level and below as compared to above the level of the organism. We term these intrinsic and emergent structures, respectively. Intrinsic structures are directly under selection, contributing to the overall performance (fitness) of the individual organism. Emergent structures involve interactions among aggregations of organisms and are not directly under selection. Given this distinction, we argue that while the functions of many intrinsic structures remain unknown, functions of emergent structures are the result of the aggregate of processes of individual organisms. We then provide a detailed and unified framework of the structure-function relationship for intrinsic structures to explore how their unknown functions can be defined. We provide examples of how these scalable definitions applied to intrinsic structures provide a framework to address questions on structure-function relationships that can be approached simultaneously from all subdisciplines of biology. We propose that this will produce a more holistic and robust understanding of how different biological functions are achieved across levels of biological organization.

Effect of clonidine on gastric emptying of liquids.

We have investigated the effects of clonidine on gastric emptying of liquids in 30 patients. In a double-blind, randomized design, clonidine 150 micrograms, morphine 10 mg or saline in 1 ml was given i.m. One hour later, the patient drank a paracetamol solution (1.5 g in 50 ml water). Venous blood samples were obtained every 15 min for 90 min thereafter. Plasma paracetamol concentrations were measured using high-pressure liquid chromatography and the area under the concentration-time curve was calculated. The degree of sedation and complications were recorded. The area under the curve for 0-60 min was significantly smaller in the morphine group than in the saline group (P = 0.002; 95% confidence interval (CI) for difference -1237 to -502 micrograms min ml-1), whereas it was greater in the clonidine group compared with the saline group, although this was not significant (95% CI for difference -423 to 1264 micrograms min ml-1). Arterial pressure was significantly lower in the clonidine group compared with the saline group. Both clonidine and morphine appeared to cause mild sedation. We conclude that clonidine 150 micrograms i.m. does not delay gastric emptying of liquids in a similar manner to morphine.

Subarachnoid block for a case of multiple system atrophy.

We report a case of multiple system atrophy in a 60-year-old man who presented twice for optical urethrotomy. Multiple system atrophy is associated with autonomic neuropathy, cerebellar ataxia, disordered control of respiration and paralysis of the abductors of the vocal cords and thus poses several problems for the anaesthetist. Subarachnoid block, which has not been described before in this group of patients, was administered twice and was well tolerated on both occasions.

Isoflurane for sedation in a case of congenital myasthenia gravis.

We describe the use of isoflurane for the management of a 3-yr-old boy with congenital myasthenia gravis who required ventilation for pneumonia. While in the intensive care unit he was sedated with isoflurane for 5 days (81 MAC-h). This provided a safe, easily controllable method of sedation which avoided the use of neuromuscular blocking agents and appeared to have no significant side effects during use. However, after it was stopped the patient developed a fine, self-limiting tremor which lasted for 2 days. Previous reports of paediatric patients sedated with isoflurane suggest that prolonged exposure may result in temporary dose-dependent neurological dysfunction, including hallucinations, ataxia and non-purposeful movements.

Cricoid pressure applied after placement of the laryngeal mask prevents gastric insufflation but inhibits ventilation.

We studied 50 patients, in a blind, crossover study, to assess if cricoid pressure applied after placement of the laryngeal mask prevented gastric insufflation without affecting ventilation. After induction of anaesthesia and neuromuscular block, a laryngeal mask was inserted and confirmed to be placed correctly. The lungs were ventilated with a maximum inflation pressure of 15 cm H2O. In the first 25 patients, expiratory volumes were measured with and without cricoid pressure (30 N). On both occasions, a free hand was placed under the patient's neck. In the next 25 patients, the effect of cricoid pressure on ventilation without support of the neck was also studied. The effect of cricoid pressure with support of the neck on gastric insufflation was then assessed using a stethoscope in all 50 patients, while the lungs were ventilated with a maximum inflation pressure of 30 cm H2O. At the end of the study, the position of the mask was re-assessed. Cricoid pressure significantly decreased mean expiratory volume (P << 0.001). This inhibitory effect was significantly greater when the pressure was applied without support of the neck (P << 0.001). Cricoid pressure significantly reduced the incidence of gastric insufflation (12 patients vs one patient; P << 0.001; 95% CI for difference 10.5-33.5%). In no patient was the mask dislodged after these procedures. Thus, although cricoid pressure applied after insertion of the laryngeal mask prevented gastric insufflation, it also decreased ventilation. The inhibitory effect of cricoid pressure on ventilation without support of the neck was greater than cricoid pressure with support of the neck.

Epidural opioids and previous caesarean section.

In the following case there was delay in diagnosing uterine rupture in a patient with an epidural in situ. The danger of using large doses of local anaesthetics and opioids epidurally in patients who have had previous caesarean sections is discussed.

Retinal fluorograms using oral fluorescein.

Sodium fluorescein may be safely administered orally. The resulting angiograms serve to document the presence or absence of dye leakage in the same manner as venous injection. The oral route of administration is of particular benefit for use in children, patients with inaccessible veins, and patients participating in studies of late retinal vascular leakage, such as postoperative cystoid macular edema. Serum concentrations of the dye plateau between thirty minutes and one hour, at levels approximating those obtained by intravenous injection.

Effects of daily oral subtoxic doses of a wet lead-based paint on cattle.

Cattle were dosed daily with a wet lead-based paint at a rate of about 6 mg of lead per kg per day for 60 weeks. The cattle did not exhibit overt symptoms of lead toxicosis. Blood and fecal samples collected during the study, and tissue samples obtained at slaughter of the animals were analyzed for lead by atomic absorption spectrophotometer equipped with a graphite furnace. Levels of lead in whole blood generally did not exceed 0.5 ppm. The residues of lead in feces reached as high as 1000 ppm. Highest residues in tissues were in calcified bone, the kidney cortex, kidney medulla, and then in liver. Residues of lead in muscle, brain, spleen, and bone marrow were similar to residues of lead in the control animal. Calves born to 2 test animals had elevated levels of lead in bone, kidney and liver.

The Movement of 2,4-dichlorophenyl methanesulfonate S in Plants.

Movement of 2,4-dichlorophenyl methanesulfonate (35)S in plant roots was investigated using plastic containers which physically isolated portions of the plant root system. Results with bean and cotton plants showed that this compound can be absorbed in one part of the root system and distributed to other parts of the root system and also to the top of the plant. These tests confirm field observations of nematode control on roots outside a treated zone which indicated lateral movement of this compound in the roots. There was no evidence of its downward movement from treated leaves to stems or roots of cotton or beans.