Water content level in inspired air on specific airway resistence in rats

The effect of increasing water content in inspired air on specific airway resistence in rats was assessed. The results show that specific airway resistances were significantly related to the water content of the inspired air, above 15.02 mg/m3, the duration of water content exposure and to the type of water nebulized. It is suggested that the increase is composed of a local and neural element caused by accumulation of mucus or mucosal swelling and changes in the composition and consistency of the mucus lining layer, respectively (AU)

Relationship between separation-age of offspring and level of arousal as an indication of behavioural disturbance

Forty Sprague-Dawley rats were separated from their mothers at 2, 3, and 4 weeks respectively and were either reared in groups or in isolation for four weeks. Spontaneous motor activity was determined in activity cages. Results showed that rats separated at 4 weeks and reared in isolation showed the highest level of motor activity. This would imply that the longer the pup spent with the mother prior to separation the greater the impact of the separation experience (AU)

Effects of ackee fruit extracts on bronchomotor tone in rats

The unripe ackee fruit, when eaten, is known to cause serious clinical manifestations, including vomiting, hypoglycaemia and acidosis. The effects, of various extracts from the arilli of the unripe fruit (including hypoglyin-A) on the lungs from rats were examined in an in vitro preparation. All the extracts were found to induce moderately severe broncho-constriction, indicating a possible contribution of these effects to the observed toxicity of ackee (AU)

A re-examination of the mechanism of ackee-induced vomiting sickness

The hypoglycemia seen in ackee poisoning almost certainly results from the presence of hypoglycin A in the aril. However, the mechanism underlying the vomiting and neurologic disorders have not been properly established. We have, in this review, re-established the latter and proposed that the vomiting and neurological features of ackee poisoning probably result from the excitotoxic properties of glutamic and aspartic acids derived directly and indirectly from ackee intake (AU)

Variation in forced expiratory volume curves of asthmatic patients with increased water content

An experiment was designed to provide information on the "safe" level of humidifiction of inspired air in asthmatic patients. It was found that air at 25 degrees celcius and 70 percent relative humidity (RH) (16.11 gm/cu m WC) and 35 degrees celcius, 40 percent RH (17.80 gm/cu m) had no significant effect on forced expiratiory volume parameters. At 25 degrees celcius, 95 percent RH (21.88 gm/cu m WC) and above changes in VC/PVC, FEV 1 and FEV 3, MMF and MBC were significantly affected (P < 0.01). Approximately 21.88 gm/cu m Water content is considered the point at which humidification of inspired air ceases to be therapeutically useful.(AU)

Altered thyroid status in marihuana-exposed male rats

The effects of marihuana exposure, particularly of THC-free crude aqueous marihuana extract (CAME) on liver gycogen, total plasma cholesterol, BMR, Raw and growth rate were studied in male Wistar rats. Liver glycogen decreased following administration of CAME and T4 (P<0.01), and increased with methimazole (P<0.01). However, marihuana smoking did not affect liver glycogen. Both marihuana smoking and CAME administration decreased the levels of plasma cholesterol (P<0.01), and methimazole increased them (P,0.01). Airway resistance decreased in rats treated with CAME, T4 and marihuana smoking and decreased with methimazole. The growth rate with marihuana exposure improved slightly (AU)

Thyroid-gonad relationship in marijuana smokers: a field study in Jamaica

Serum concentrations of thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), T3 uptake (T3U), free thyroxine index (FTI) and testosterone were studied by radioimmunoassays to elucidate thyroid-gonad relationship in 26 male marijuana smokers in Jamaica. Serum T3 levels were significantly lower (p<0.05) in smokers compared with non-smokers, whereas serum T4, TSH, T3U, FTI and testosterone levels were found to be within normal limits. Decrease in serum T3 levels has been attributed to ingestion of tetrahydrocannabinol in addition to other factors associated with marijuana smoking. Such a profile of thyroid hormones, with no change in TSH, is suggestive of euthyroidism in smokers. The study also did not indicate any alteration in the pituitary-thyroid-gonad axis in chronic marijuana smokers (AU)

Thyroid-gonad relationship in bronchial asthma

Serum concentrations of thyroxine (T4), triodothyronine (T3), thyrotropin (TSH), T3 uptake (T3U), free thyroxine (FT4I) and free triodothyronine (FT3I) indices and testosterone (T) were studied by radioimmunoassays to elucidiate thyroid-gonad relationships in 30 men of African origin with bronchial asthma. In asthmatic subjects, (i) there were decreases (p<0.001) in both serum T3, FT3I and T levels;(ii) significant increases (p<0.001) in T3U were not associated with changes in serum T4 and FT4I, indicating an abnormality in thyroid-binding globulins (TBG); and is concluded that the hypophyseal-thyroid-gonadal axis may be set at a lower level in asthmatic patients (AU)

Thyroid function in dengue fever, meningitis, encephalitis, poliomyelitis and other febrile conditions

Thyroid function was studied by estimating serum thyroxine (T4), triodothyronine (T3) and thyrotropin (TSH) in 52 patients suffering from dengue fever, bacterial meningitis, viral encephalitis, paralytic poliomyelitis and other febrile illnesses. Mean serum concentrations of total T4 and T3 were significantly lower in all patients except those suffering from poliomyelitis. Serum TSH was significantly low in dengue fever and pyrexia of unknown origin (PUO). Though the TSH levels were also low in patients with bacterial meningitis and encephalitis, the differences were not statistically significant. Decreases in serum T4, T3 and FT1 in severe illnesses as compared to normal subjects may signify a state of secondary hypothyroidism of a functional type. It will be erroneous to say that decreases in T4 and T3 in systemic illnesses is entirely an adaptive or protective process to maintain metabolic rate. The possible value of thyroid hormone replacement therapy in these illnesses needs further investigations. (AU)

Factors contributing to increased airway resistance with over humidification of inspired air - abstract

Inhalation of air containing increased water content has been shown to cause increased specific airway resistance (sRaw). It has been postulated that these changes might be related to reflex broncho-constriction and/or mucosal swelling. We attempted to elucidate the exact mechanism of action by a series of studies in rats, designed to demonstrate whether changes in specific airway resistance (as measured by whole body plethysmography), due to inhalation of air saturated with distilled water or tap water were preventable or reversible by either sympathomimetic (adrenaline), parasympatholytic (atropine) or mucolytic (N-acetyl cysteine) drugs. The results obtained showed that inhalation of air containing either tap or distilled water above the "safe level" (15.02gm/m(to the 3rd power) of humidification caused a significant increase in specific airway resistance above the control (p<0.01), with a slightly greater increase with tap water. Administration of adrenaline in aerosol to inspired air containing distilled or tap water vapour for six minutes caused no significant change in sRaw. A significant decrease in sRaw was obtained by injecting intramuscularly atropine (p0.01): and administration of N-acetylcysteine with inspired air containing distilled or tap water vapour caused an increase in sRaw above inhalation containing only tap or distilled water vapour, (p<0.05) which decreased with suction (p<0.05). Likewise N-acetyl cystine with distilled water or tap water vapour caused a significant increase in sRaw above that of inspired air with tap or distilled water alone (p<0.05) which significantly decreased with administration of atropine. These results suggest that mucosal swelling, reversible by parasympatholytic therapy, is a major factor in the increased specific airway resistance with over humidification of inspired air. There is no convincing evidence that broncho-constriction is of major importance. Mucolytic agents may aid in decomposing mucus but their effect on sRaw appears to be negative unless the decomposed products are moved by coughing or suction, and may be dangerous in patients who have no cough reflex (AU)

Relation of specific airway resistance to water content in inspired air in rats - abstract

Recent evidence has shown that increased humidification of inspired air increases airway resistance in healthy subjects and in patients with repiratory disease, and may produce gross pathological changes in the lungs. Ambient air (22§C, 50 percent relative humidity, 9.71 gm./m (to the 3rd power) water content) is assumed to be saturated and at body temperature by the time it reaches the tracheal bifurcation, so that any saturation deficit must exist only in small segments between the nasal or if ice and the main bronchi. Increasing the water content of inspired air should not theoretically affect airway resistance unless the air is incompletely saturated at the bifurcation, as assumed, and hence evaporative loss of water and heat from the mucosa is reduced with increased humidification of inspired air. This study, therefore, attempted to find out the lowest water content that would cause significant changes in specific airway resistance(sRaw) in rats by selectively increasing the water content of inspired air from 9.71 to 26.52gm./m (to 3rd power). sRaw was measured by whole body plethysmography. At water contents varying from 9.71 to 12.81gm./m (to 3rd power), however, sRaw showed a positive correlation with increased water content (p<0.01). Since increased water content can only be achieved by increasing the temperature, the effect of temperature on sRaw at a constant water content was investigated. At a constant water content of 12.7gm/m(to3rd power) mean sRAw did not change significantly from the control over a temperature range from 22 to 33§C. With water contents of 15.42, 17.48 and 19.53 gm./m(to 3rd power over the same temperature range, however, the mean sRaw increased significantly (p<0.01). Three factor analysis of variance showed that sRaw was significantly dependent on water content (p<0.01), the length of the exposure (p<0.01) and the type of water (p<0.01), since a significantly greater response was obtained with tap water. It is concluded that the transition point for significant changes in sRaw in rats is 15.02gm./m(to 3rd power) (22§C, 75 percent relative humidity). Increases above this level may be related to mucosal swelling and bronch-constriction. It seems that the repiratory system is adjusted to constantly eliminate some water, and interference with this function by overhumidifying the inspired air compromises pulmonary function. These findings may have implications in inhalation therapy of patients (AU)

Critical anatomical site in healthy subjects from observation of forced expiratory volume curves with external resistances

The internal diameter of the air passages narrows from the trachea to the periphery of the lungs. Because of this it should be possible to predict the site at which the greatest change in resistance would occur for a given flow rate using the orifice flow equation (P = p/Cý(1/A2ý 1/A1ý) Vý where p = density of air, C = discharge constant which depends on the roughness of the tube and on Reynolds number, V is the volume rate of flow and A1 and A2 are the cross sectional areas) and compare it with forced expiratory volume curves (FEV) in healthy subjects. Theoretical calculations showed that the 3rd-6th generation of the bronchial tree contributed about 40 percent to the total airway resistance. Direct measurements by previous workers showed that approximately 55 percent of the total pulmonary resistance was contributed by the 3rd-6th generation i.e. 3-6 mm internal diameter bronchi. Results of FEV curves in normal subjects against external resistance of known internal diameters will be presented. These results show that the critical orifice (i.e. the point at which greatest inflection begins in the FEV curve) is in the range of 6-9 mm internal diameter (around the 3rd generation of the tracheobronchial tree). An analog of the tracheobronchial tree is being prepared to simulate the resistance to breathing, and thereby provide a simple method of measuring airway resistance (AU)

Airway constriction in asthmatics determined from forced expiratory volume curves with external resistances

This study was undertaken to determine what role the level of bronchial constriction played in the dyspnoea of the asthmatic attack. Forced expiratory volume curves (FEV) of asthmatic patients were studied with and without external resistances (discs) of known internal diameters, during an attack, after bronchodilator therapy and during remission. The results show that the site of narrowing of the tracheobronchial tree was important. This "critical site" accounts for approximately 20-40 percentof the calculated equivalent resistance in an attack. From the matched FEV curves with external resistances it was observed that discs with internal diameters of 1.5-5.0 mm most frequently matched the asthmatic curve. On recovery disc of 5.0-9 mm matched the patient's curve. The data supports previously reported studies based on theoretical calculations and direct measurements which showed that the critical resistance to respiration occurs around the level of the 3rd-6th generation of the tracheobronchial tree with internal diameters of 3-8mm; it is of interest to note in this repect that endotracheal tubes have internal diameters in this same range (AU)

Altered thyroid status: a possible cause of growth retardation in children with congenital heart disease

To investigate the possibility that growth retardation in children suffering from congenital heart disease (CHD) may be due to altered thyroid function, we studied 27 growth-retarded children with CHD (7 cyanotic, 20 acyanotic) and compared the results with thyroid functions of 10 healthy normal-growing children of the same age group (control). Serum tri-iodothyronine (T3) and throxine (T4) levels were significantly lower in cyanotic CHD; however, serum thyrotropin (TSH) levels were not affected. In acyanotic children, thyroid function was essentially normal. These findings suggest that subnormal levels of T3 and T4 with normal TSH might be a homeostatic response to chronic hypoxia in cyanotic CHD and may contribute to growth retardation in these children (AU)

Chronic effects of marihuana extract on thyroid-gonad relationship in rats

Studies were carried out to elucidate the effects of Crude Aqueous Marihauna Extract free of tetrahydrocannabinol and other cannabinoids (CAME) on thyroid-gonad relationship in male rats. Oral indigestion of CAME for 52 days increased (p<0.01) the plasma levels of total circulating thyroxine and triiodothyronine, increased the weight of the adrenal gland (p<0.05), slightly decreased the plasma thyrotrophin level and the weight of the thyroid gland. These changes suggest the presence of hyperthyroidism in rats receiving CAME. Increased plasma thyroxine levels in CAME-treated rats correlated with the total plasma testosterone (r=0.526), indicating a possibility of thyroid-gonad relationship in such rats (AU)

Interaction of dopamine agonists with disrupted mesolimbic pathways implications for mental health

This work was designed to evaluate, in conjunction with certain dopamine agonists, the effects of disruption of the mesolimbic system on spontaneous motor activity and stereotype. The results indicated that lesions to the nucleus accumbens produced increments in motor activity that were exacerbated by amphetamine (5.0 mg/kg). Administration of apomorphine (1.0 mg.kg) produced similar results but was not as effective as amphetamine in inducing motor dysfunction. The relevance of these findings to psychopathology and motor disorders is discussed, with implications for public health policy (AU)

Thyroid-gonad relationship in chronic renal failure

Thirty-four men of African origin suffering from chronic renal failure, (CRF) were studied to assess thyroid functions and their relationships to serum testosterone. Significantly lower mean values of T4, T3, testosterone, FT4I and FT3I were observed in CRF patients as compared to those in 23 healthy control subjects. Serum TSH, LH and TBG did not differ significantly whereas T3U and PRL were higher in CRF patients. Mean serum T4, T3U and FT4I values were further reduced in haemodialysed than in nonhaemodialysed patients. Significant positive coefficients of correlation between thyroid hormones and testosterone were observed in CRF patients. Simultaneous decreases in both serum and testosterone in the presence of normal serum TSH, LH and TBG levels suggest dysfunction of the pituitary-thyroid-gonad axis (AU)

Tracheobronchial function in health and disease: effect of mucolytic substances

The effect of mucolytic and expectorant substances on ciliary beat frequency, mucus transport velocity and mucus production, was investigated in normal and bronchitic rats. The results showed that: (i) N-acetylcysteine and S-carboxymethylcysteine were mildly cilioexcitatory at low and ciliodepressive at higher concentrations in both normal and bronchitic rats. A similar pattern was seen in mucus transport velocity. (ii) Bisolvan enhanced all aspects of muciciliary activity in both groups of animals. Sobrepin was less effective than Bisolvan and more effective than Tachoquilin. (iii) Geleomytrol, Ozothin and prostaglandin E1 were all cilioexcitatory in rats with bronchitis. Mucus transport velocity was similarly stimulated by both Geleomyrtol and Ozothin. (iv) Ammonium chloride and potassium iodide enhanced mucociliary activity in normal and bronchitic rats. (v) All substances stimulated mucus production, however, the most potent was prostaglandins E1. The mechanisms for increased mucociliary activity involve inter alia the probable cleaving of disulphide bridges, decreased mucosal swelling, altered rheological characteristics and stimulation of adenylate cyclase (AU)

Direct determination of luminal diameter changes in intrapulmonary airways

A method is decribed for the direct measurement of changes in luminal diameter at all levels of the airway. Using this method it was found that (i) abrupt bronchiolar collapse occurred in the preterminal and terminal bronchioles once the luminal diameter was reduced to a critical level: (ii) decreased temperatures resulted in airway narrowing which was reversed by increasing the temperature to above 25 degrees C; as a rule, airway narrowing followed a cranial to caudal direction, and higher concentration of a drug being required to close the peripheral airways; (iii) bronchodilators except Carbuterol had no effect on resting bronchial tone or on acetylcholine-induced constriction in the absence of O-adrenoreceptor blockade; (iv) at 35 degrees C rhythmic waves (frequency 6--20/min) were observed; these waves travelled from the periphery in a cranial direction. (AU)

Contractile response of uterine smooth muscle to acetylcholine and marijuana extract

Marijuana extract (ME) is known to influence smooth muscle activity. This study was designed to investigate the effect of crude ME on rat uterine muscle and to explain the mechanism of action using antagonists such as atropine, ergometrine and propranolol. The contractions and the electrical activity were recorded on isolated superfused rat uteri. It is speculated that ME by its uterine stimulation action compromise uterine blood and may affect oxygen/nutrient transfer. The implication of this to the fetus is discussed. (AU)