An in vitro approach to study chromosomal DNA damage

In this study a simple electrophoresis approach has been proposed for assessing DNA damage per chromosome in vitro. Novel procedures of gel casting, sample loading, electrophoresis and quantification of damage have been suggested. Sets of Saccharomyces cerevisiae chromosomes subjected to DNA damage by Bleomycin, Co60-gamma-radiation alone and in combination with Hoechst were studied in detail. Statistical analyses showed that damage induced by Bleomycin bore linear positive correlation with %GA (r = 0.97) and %GT (r = 0.61) contents of chromosomes. Samples pre-treated with Hoechst showed much less damage by Co60-gamma-irradiation as compared to samples not treated with Hoechst but exposed to Co60-gamma-irradiation. The 'protective effect of Hoechst' bore linear positive correlation (r = 0.8) with %TAT content of chromosomes.

Measurements of sulfur dioxide and formaldehyde in Taipei using a differential optical absorption spectrometer

Taipei, the capital city of Taiwan, lies in a basin, and its topography prevents the dispersion of pollutants in the city. As a continuation of our air quality study, from February 1999 through June 1999, we measured the concentrations of SO2 at six different locations and of formaldehyde at five locations using a differential optical absorption spectrometer (DOAS). The average concentration of SO2 varied from 3.5 to 6.6 ppb. The average concentration was highest at Toucheng because of its proximity to point sources. The level in Hsientien was close to that in Toucheng, with Hsinyu showing the lowest concentrations. The DOAS and the Taiwan Air Quality Monitoring Network (TAQMN) measurements for SO2 were highly correlated (r2 > 0.9) for Toucheng, Panchiao, and Hsientien. However, DOAS SO2 concentrations were 2 times higher for Hsientien and slightly lower for Panchiao than the TAQMN concentrations were. The average concentration of formaldehyde varied from 7 to 10 ppb. Diurnal variation of formaldehyde closely followed the variation of ozone, especially when the 1-hr peak ozone concentration was > 60 ppb. Photochemical formation accounted for the ambient levels of formaldehyde in Taipei. Concentration of formaldehyde became significant on days when O3 concentration was high. Our results indicate that DOAS can replace conventional measurement techniques.

Decreased activity of the L-arginine-nitric oxide metabolic pathway in patients with congestive heart failure

BACKGROUND

Impaired endothelium-dependent, nitric oxide (NO)-mediated vasodilation may contribute to increased vasomotor tone in patients with heart failure. Whether decreased endothelium-dependent, NO-mediated vasodilation in patients with heart failure is due to decreased synthesis or increased degradation of NO is unknown.

METHODS AND RESULTS

To specifically assess the synthetic activity of the L-arginine-NO metabolic pathway, urinary excretion of [15N]nitrates and [15N]urea was determined after a primed continuous intravenous infusion of L-[15N]arginine (40 micromol/kg) in 16 patients with congestive heart failure and 9 age-matched normal control subjects at rest and during submaximal treadmill exercise. After infusion of L-[15N]arginine, 24-hour urinary excretion of [15N]nitrates was decreased in patients with congestive heart failure at rest (2.2+/-0.5 versus 8.0+/-2.3 micromol/24 h) and during submaximal exercise (2.4+/-1.2 versus 11. 4+/-4.0 micromol/24 h) compared with control subjects (both P<0.01). After infusion of L-[15N]arginine, 24-hour urinary excretions of [15N]urea at rest in patients with congestive heart failure and control subjects were not different (1.1+/-0.3 versus 1.2+/-0.2 mmol/24 h, P>0.20).

CONCLUSIONS

A specific decrease in synthetic activity of the L-arginine-NO metabolic pathway contributes to decreased endothelium-dependent vasodilation in patients with congestive heart failure.

Cardiovascular responses to application of lower body negative pressure of male volunteers in seated position

Lower body negative pressure (LBNP) has been used to evaluate orthostatic tolerance and for studying the effects of +Gz induced physiological strain and hence has great practical significance in aerospace medicine. Cardiovascular responses in man on application to LBNP (-40 mmHg) in seated (upright) position in a specially designed LBNP chamber have been studied in eight normal healthy male volunteers between the age group of 25-36 yrs. They were subjected to -40 mmHg negative pressure in steps of -10 mmHg for a duration of 5 min each. The total duration of the experiment was 20 min. Heart rate (HR), blood pressure (BP) Cardiac output (CO) were measured and mean blood pressure (MBP) and total peripheral resistance (TPR) were computed. The results indicate a significant increase in HR (P < 0.01), SV (P < 0.01). Studies on limited number of subjects on application to LBNP (40 mmHg) in supine position have also been carried out and compared with the physiological strain induced in subjects in seated position. Study of HR, SV, CO, responses of the subjects on exposure to LBNP in seated position elicit similar response in subjects exposed to +Gz stress as reported by other workers. It is concluded that LBNP technique can be used to study the effects of +Gz induced physiological strain in man.

Calcium sensitising agents in heart failure

Congestive heart failure (CHF) is a common cardiovascular disorder that is characterised, in part, by a decreased cardiac output reserve. Accordingly, there is ongoing interest in the role of positive inotropic agents (e.g. adrenergic agonists and phosphodiesterase type III inhibitors, which mediate their cardiovascular effects via a cyclic adenosine monophosphate-dependent mechanism) in the treatment of CHF. However, enthusiasm for positive inotropic therapy in CHF has been dampened by the results of clinical trials, which have shown that these drugs are associated with an increased risk of mortality. Calcium sensitising agents are a heterogeneous group of positive inotropic agents that mediate their cardiovascular actions (at least in part) by increasing the sensitivity of the contractile elements to calcium. Increased sensitivity to calcium may be related to changes in calcium binding to troponin C, or to direct effects on the actin-myosin complex. In addition, the inhibition of phosphodiesterase type III may contribute to the positive inotropic action of calcium sensitising agents. Five agents with calcium sensitising properties (pimobendan, levosimendan, MCI-154, EMD-53998 and CGP-48506) have been studied as possible therapies for CHF. All of these agents have demonstrated a positive inotropic action in isolated cardiac tissue and in animal models of CHF. In clinical trials, pimobendan, the most extensively studied of these drugs, was well tolerated and was associated with improved exercise tolerance during the first 6 months of therapy; however, it was also associated with a nonsignificant trend towards increased mortality. Because many of the calcium sensitising agents also inhibit phosphodiesterase type III activity, the long term safety of these agents is uncertain. Large-scale survival trials are required to determine the long term safety and efficacy of these agents before their role in the treatment of CHF can be defined.

Effect of amine activators on the properties of chemical cured dental composites

The purpose of this study was to evaluate the reactivity and the effect of concentration of three tertiary amines upon the mechanical properties of a chemical curing dental composite. Chemical cured composite pastes were prepared by keeping peroxide concentration constant at 1 wt% (by weight of resin mixture) and by varying the amine/peroxide molar ratio from 0.25 to 1.5. Composite samples were prepared for all three amine pastes aged for 1, 15, 30, 45, and 60 d stored at 8, 22, and 37 degrees C. The loss in activity of the tertiary amine with time was measured. Changes in compressive strength, diametral tensile strength, and microhardness were also measured. A sharp decrease in working and setting times corresponding to increased activity was noticed with an increased amine content. The activity was found to vary in the order N,N-dimethyl p-toluidine (DMPT) > 2-(4-dimethylaminophenyl)ethanol (DMAPEA) > N,Ndiethanol p-toluidine (DEPT). DMPT is found to be more temperature sensitive than DMAPEA and DEPT. However, DEPT is found to provide better storage stability out of all three amines tested. Each amine was found to possess optimum concentrations at which the mechanical properties showed maximum values. DEPT is preferred for long-term storage stability in chemical-cured dental composites where aging tends to reduce the activity of the amine.

Survey of the practice of electroconvulsive therapy in North Carolina

A survey of North Carolina hospitals was conducted to determine the distribution and characteristics of facilities that offer electroconvulsive therapy (ECT). Parameters examined in the survey included bed size, geographic location, and average volume of ECT treatments. Facilities that offer ECT make up only 14% of total hospitals surveyed. The majority of hospitals with ECT services are located in moderate to large urban areas. Specific areas of practice were surveyed for each facility, including type of ECT device, location of treatments/recovery, methods for monitoring ictal motor seizure, time required to perform treatments, staffing, and potential areas of ECT nursing education. Standard practices at facilities were found to be generally in compliance with American Psychiatric Association recommendations; differences in practices were identified. Potential nursing education topics related to ECT were ranked to determine those most useful to individual nursing staffs.

State of the art: nursing knowledge and electroconvulsive therapy

Nursing services attempting to develop standards for their own facilities will find limited literature specific to nursing and electroconvulsive therapy (ECT) in American publications. From 1966 to December 1994, there were only 19 publications in American nursing journals that provide a specific focus on nursing and ECT. Only one of these articles reported research findings. Twenty-seven citations in Convulsive Therapy included nurse contributors. While the APA Task Force on the Practice of ECT has addressed educational needs of nursing and technical elements of the procedure, there do not currently exist specific standards for nursing practice in ECT. Concerns salient to nursing that have generated articles by nurses include instruction of patients, support to patients and families, safety of patients, assessment of clinical status, informed consent, and nurses' and patients' attitudes about ECT. Nurses are encouraged to join their physician-colleagues in developing and disseminating the information needed for the field of nursing to contribute its own expertise to the care of patients receiving ECT.

Destructive skeletal lesions as the primary initial manifestation of acute childhood leukemia

Bony involvement in leukemia has been long recognized in the medical literature. However, severe osseous changes, as the sole initial manifestation of childhood leukemia is a unique feature of the case reported here.

Seroepidemiology of rubella in Bahrain

Although the Ministry of Health of the State of Bahrain has set priorities for vaccination against a number of communicable diseases including the six target diseases of the Expanded Program of Immunization, no such policy for rubella immunization exists. The incidence of rubella in Bahrain is not precisely known nor is the magnitude of the problem of Congenital Rubella Syndrome. A survey of schoolchildren and primigravidae attending antenatal clinics was undertaken in Bahrain to determine the level of natural immunity against rubella in these groups, which we hope would help us in formulating a vaccination policy. We have found that 67.8% of the 6-7 year old children are susceptible to rubella and that by the age of 18 years susceptibility drops to 10.4%. The decrease in susceptibility was significant until the age of 14 years after which the change became minimal. Efforts should ideally be focused on immunizing all susceptible females before they get married. However, at present, it would be more economical to vaccinate all girls premaritally than to screen and vaccinate those susceptible. When a cheaper screening test for assessing immunity against rubella becomes available, a policy of premarital and post-partum screening followed by vaccination of susceptibles should be put into practice.

Pulmonary function of Indian athletes and sportsmen: comparison with American athletes

Studies were conducted to evaluate pulmonary functions in Indian athletes and sportsmen associated with different athletic events and games. It was found that swimmers were having significantly higher vital capacity (VC) and forced expiratory volume (FEV1) values than all other athletic groups studied. Results have been discussed keeping in view the physiological, functional and structural demands in various events. Pulmonary function values of Indian athletes have also been compared with American athletes of standardized height for a better appraisal of athletic potentiality in our athletes. The importance of athletic training from childhood have been ascribed to be the reason for superior lung volumes and capacities in US athletes.

Physiological factors associated with the success in marathon running

Marathon running is the most gruelling athletic event in international sport. Success of well trained athlete largely depends upon his perfect coordination of movements in relation to speed and optimum physiological adjustments. In order to identify the physiological factors which play crucial contributory role in successful marathon runners an evaluation study was conducted on 7 successful Indian athletes from among many competitors. Results of the study were compared between the 1st and the 7th rankers vis-a-vis the world champion in this event. Results indicated that the maximal aerobic power and economy in 'work' involved in marathon running were most important factors for the success in this event. In addition, a comparison of the blood lactic acid level of Indian with that of the world champion revealed that the latter could sustain at 85% of his maximal aerobic power for 2 hours compared to 78% and 62% of 1st and 7th ranker Indian athletes. There was not much of a difference between the world and Indian champion in this respect. Further, thermoregulatory efficiency was also found to play an important contributory role in determining success in this event. It is considered that a suitable index incorporating all the above factors is likely to be the most appropriate screening procedure in the evaluation programme of marathon runners for the reasons as discussed.

Chemoreceptor sensitivity in adaptation to high altitude

Studies were carried out in a group of 20 young male subjects to investigate the changes in chemoreceptor sensitivity during acclimatization to altitude. Their hypoxic sensitivity and carbon dioxide sensitivity were studied at Delhi, during acclimatization at 3500 m, and on return to sea level. Similar studies were also done in a group of 10 acclimatized lowlanders who stayed at 3500-4000 m for 12-14 months, and also on 10 high-altitude natives. The results showed no significant alteration in the hypoxic sensitivity of the lowlanders; but CO2 sensitivity was markedly elevated at altitude, both in sojourners and acclimatized lowlanders. The high-altitude natives showed less sensitivity to hypoxia, whereas the CO2 sensitivity was normal.

Chemoreceptor sensitivity and maladaptation to high altitude in man

Studies were carried out to find out the role of chemoreceptor sensitivity in the causation of maladaptation syndromes on acute exposure to altitude. The experiments were done in two phases. In phase I, the responses in chemoreceptor sensitivity were studied in altitude acclimatized subjects and compared with those who suffered from either High Altitude Pulmonary Oedema (HAPO) or Acute Mountain Sickness (AMS). In Phase II, a similar comparison was done in two groups of subjects, one representing normal sojourners at 3,500 m and the other being subjects who had just recovered from HAPO. The first phase was done at Delhi; and the second at an altitude of 3,500 m. Parameters of assessment were hypoxic sensitivity, carbon dioxide sensitivity, ventilation (VE), respiratory frequency (Rf), forced vital capacity (FVC), forced expiratory volume at the first second (FEV1), heart rate (HR), blood pressure (BP), and oral temperature (Tor). The results showed significantly lower sensitivity to both hypoxia and carbon dioxide in maladapted subjects, as compared to those who were acclimatized in both the categories suggesting thereby that reduced chemoreceptor sensitivity might be an initiating factor in the causation of maladaptation syndromes at altitude.