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Biomedical subjects

D R Jones

Publications and source records attributed to D R Jones.

At least 217 records · Page 12Linked to original sources
PubMed1991

The effect of brain transection on the response to forced submergence in ducks.

The effect of brain transection at two levels on cardiovascular responses to forced submergence has been investigated in ducks. Compared with intact ducks, neither decerebration nor brain stem transection at the rostral mesencephalic (RM) level had any effect on development of diving bradycardia, or heart rate at the end of two-min dives. Arterial blood pressure was maintained in brain transected ducks as well as in intact ducks. Furthermore, end-dive arterial blood gases and pH were also similar in intact and brain transected ducks confirming that the oxygen sparing cardiovascular adjustments, involving a massive increase in total peripheral resistance, were unimpaired by brain transection. In this respect, ducks with RM transections tolerated four-min dives. However, the increase in post-dive VE seen in intact and decerebrated ducks was prevented by RM transection. We conclude that control of the circulatory response to diving resides in the lower brainstem, is reflexogenic in nature, and does not depend on the cognitive perception of 'fearful' stimuli.

Animals↗
PubMed1991

The value of duplex scanning with venous occlusion in the preoperative prediction of femoro-distal vein bypass graft diameter.

The diameter of the long saphenous vein has been shown to affect the outcome of femoro-distal bypass. Many surgeons regard a vein with a diameter of less than 3 mm as being unsuitable. The long saphenous vein was studied in 35 patients undergoing femoro-distal bypass. Diameter measurements of the vein were performed using an ATL duplex scanner at the groin, mid-thigh and knee. Measurements were performed preoperatively both at rest and with a venous occlusion cuff to dilate the vein, and subsequently at 7 days and 2 months after implantation. The mean diameter of the vein at the mid-thigh was 4.1 mm non-dilated, 5.1 mm with occlusion, 5.0 mm 7 days postoperatively and 5.2 mm at 2 months (ANOVA, p less than 0.05). The mean diameter of the vein at the knee was 3.9 mm non-dilated, 4.8 mm with occlusion, 4.8 mm at 7 days and 4.9 mm at 2 months after operation (ANOVA, p less than 0.025). In all five patients whose preoperative resting vein diameter at the knee or mid-thigh was less than 3 mm, preoperative dilatation occurred, such that the diameter became greater than 3 mm. These results suggest that by using a technique of venous occlusion at the time of pre-operative vein mapping, the functional diameter of the vein can be predicted and vein utilisation may be increased.

Aged↗
PubMed1991

Mortality rates from multiple sclerosis: geographical and temporal variations revisited.

A review of the United Kingdom (UK) multiple sclerosis (MS) literature suggests that over the last three decades prevalence and estimated incidence rates have increased, while mortality rates have been declining. UK mortality data over a 30 year period have been studied to examine temporal and geographical variations, to estimate changes in survival, and to examine the relationship between mortality and morbidity trends. The study has shown an overall decline in mortality throughout the UK of approximately 25% over the 30 year period ending in 1983, and a reduction in the mortality differential between Scotland, and England and Wales, but no positive correlation has been found between mortality and morbidity. The overall decline in death rate in females was 23% and in males 30% over the 30 years of the survey. The total number of deaths declined by 39% between the five year periods 1954-58 and 1979-83 in Scotland compared with a 10% decline for England and Wales. Estimated median age of death increased from 52 to 59 years and the improvement in survival over the period of study was similar for both countries and is unlikely to have contributed to the reduction in mortality differential. Within England and Wales regional mortality rates did not show a clear north-south gradient. The decline in the mortality differential between Scotland and England (if not artefactual) may provide an important aetiological clue in the search for the cause of multiple sclerosis, and the rate of decline suggests an environmental rather than a genetic aetiology.

Adolescent↗
PubMed1991

Role of adrenal catecholamines during forced submergence in ducks.

Maximum underwater tolerance (UTmax) of chronically adrenalectomized ducks (ADX, 5.3 +/- 0.3 min) and chronically adrenal-denervated ducks (DNX, 7.2 +/- 0.2 min) was significantly lower than sham-operated controls (SH-ADX, 10 +/- 0.8 min; SH-DNX, 12.2 +/- 0.5 min). After 4 min forced submergence, heart rates of ADX (62 +/- 16 beats/min) and DNX (31 +/- 2 beats/min) ducks were significantly higher than in their respective sham-operated controls (23 +/- 3 and 17 +/- 2 beats/min), although their blood pressure was significantly lower. Arterial partial pressure of O2, arterial O2 content, arterial pH, and lactate levels in DNX ducks (42 +/- 2 mmHg, 4.5 +/- 0.8 ml O2/100 ml blood, 7.233 +/- 0.016, 3.1 +/- 0.3 mM, respectively) were significantly lower than in SH-DNX ducks after 5 min forced submergence (53 +/- 1 mmHg, 6.8 +/- 0.4 ml O2/100 ml blood, 7.301 +/- 0.007, 4.8 +/- 0.4 mM, respectively). Venous infusion of catecholamines in ADX and DNX ducks during forced submergence significantly increased UTmax. It is suggested that adrenal catecholamines increase tolerance to underwater submersion by enhancing peripheral vasoconstriction, thus preserving the O2 stores for the heart and brain. Other adrenal products could also be involved.

Adrenal Glands↗
PubMed1991

Neural and humoral effects on hindlimb vascular resistance of ducks during forced submergence.

Circulating catecholamines increase by three orders of magnitude in forced submerged ducks; their role in promoting vascular resistance was studied using vascular perfusion of hindlimbs. Perfusion pressure and blood flow were recorded simultaneously in hindlimbs of ducks during forced submergence. One leg was perfused with blood mixtures devoid of catecholamines (test leg) and compared with the other autoperfused leg. Perfusion pressures in test legs perfused with hyperoxic and hypocapnic blood or with hypoxic and hypocapnic blood were not significantly different from those in the matching autoperfused legs. However, when test legs were perfused with hypercapnic blood, regardless of whether blood was hypoxic or hyperoxic, perfusion pressures were significantly lower than in autoperfused legs. Adding catecholamines to test legs perfused with hypoxic and hypercapnic blood, after 3 min submergence, significantly enhanced vasoconstriction. Hypercapnia acts directly on the peripheral vascular beds and impairs the neurally mediated vasoconstriction during submergence, while circulating catecholamines restore peripheral vasoconstriction. Thus circulating catecholamines are needed to compensate for the depressant action of hypercapnia on neurally mediated vasoconstriction.

Animals↗
PubMed1991

Differing renal effects of activated and nonactivated isoelectric peaks of human prorenin in rats.

Isoelectric species of renin are physically heterogeneous. Recent evidence suggests that they may differ functionally, with some species producing natriuresis and diuresis, whereas others have no effect. A physiological function of secreted prorenin has not been documented in any species. The present study was designed to confirm and describe for the first time the renal effects of certain isoelectric species of prorenin. Anesthetized Sprague-Dawley rats were injected (0.1 ml) with trypsin-activated or nonactivated prorenin obtained from human ovarian follicular fluid. The dose chosen was calculated as sufficient to produce 2,300 ng angiotensin I.h-1.100 g rat body wt-1 in the presence of excess sheep substrate. Blood pressure, creatinine clearance, urine flow rate, and urine sodium, potassium, and osmolar excretion were measured. Activated prorenin from isoelectric peaks at isoelectric points (pI) 5.1, 5.2, 5.4, and 5.6 produced marked increases in urine volume (sixfold) and sodium excretion (7- to 10-fold) compared with the group receiving the vehicle (1% albumin in 0.9% saline). Activated prorenin from peaks at pI 4.9 and 5.8 produced no significant increase over the vehicle-only experiments. Captopril pretreatment (1 mg/kg iv) completely blocked the effects of peaks at pI 5.4 and 5.6. Interestingly, injection of nonactivated prorenin from peaks at pI 5.4 and 5.6 produced effects similar to the injection of activated prorenin from these peaks. Similarly, this effect was blocked by pretreatment with captopril. In summary, only certain isoelectric peaks of human prorenin whether activated, to active renin, or nonactivated produced a marked natriuresis and diuresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Audit of attitudes to and use of postoperative thromboembolic prophylaxis in a regional health authority.

A survey of usage and attitudes to thromboembolic prophylaxis among 46 general surgeons in the Mersey Region found that 87% use either low-dose heparin, graduated compression stockings or both on a regular basis for their major cases. However, there was a wide variation of usage: 9 (19.6%) always used heparin in combination with thromboembolic stockings, 4 (8.7%) always used heparin alone, no surgeon used thromboembolic stockings alone. A total of 18 (39%) used thromboembolic stockings in combination with heparin, one-half of them selectively. A further 24% of surgeons used either low-dose heparin or thromboembolic stockings or both on selected patients. Current literature beliefs concerning the efficacy of low-dose heparin and thromboembolic stockings showed a similar variation, with 13% of surgeons believing that the efficacy of low-dose heparin against postoperative deep vein thrombosis has not been shown, 22% believing that thromboembolic stockings were ineffective against postoperative deep vein thrombosis, and 24% believing that low-dose heparin was of no value as a prophylactic agent against postoperative pulmonary embolism. Published meta-analysis has shown these beliefs to be wrong.

Attitude of Health Personnel↗
PubMed1991

A review of central nervous system effects of G-induced loss of consciousness on volunteer subjects.

A review of the literature on the central nervous system (CNS) effects of repeated centrifuge acceleration studies involving G-induced loss of consciousness (G-LOC) reveals that remarkably few adverse effects have been reported, aside from the G-LOC itself, even in subjects with numerous exposures. However, most of the followup studies were performed before the availability of sophisticated neuropsychological tests and non-invasive means of imaging the CNS, such as computerized tomography (CT), magnetic resonance imaging (MRI), brain electrical activity measurement (BEAM), and positron emission tomography (PET). Further, only a handful of long-term followup studies have been done. Thus, although repeated G-LOC may have induced some long-term adverse CNS effects, either organic or functional, little has been done to detect them. Even granted that some damage may be done, this risk must be weighed against the risk of aviators of similar damage from high +Gz exposures in flight, and even more against the risk of fatal G-LOC aircraft accidents. Volunteers for centrifuge acceleration studies should be fully informed about what is known and not known in this regard. As an ancillary measure, head restraints may be useful in avoiding postural trauma to the cervical spine, or impact injury to the head when G-LOC occurs and the head snaps forward and down.

Acceleration↗
PubMed1991

The successful resuscitation of a hypothermic multitrauma patient.

Accidental hypothermia due to exposure is an infrequent cause of circulatory arrest. A premature diagnosis of clinical death must be avoided in these patients and vigorous attempts at active rewarming are indicated. Extracorporeal circulation in the form of partial cardiopulmonary bypass has been reported as an effective means of rapid, even core rewarming. We wish to report a recent case at Ruby Memorial Hospital in which extracorporeal circulation was used successfully in resuscitating a profoundly hypothermic multi-trauma victim.

Accidents, Traffic↗
PubMed1990

Sepsis of vascular catheters. II: In vitro disinfection of colonized tubing.

Preparatory to development of in situ disinfection of implanted catheters, silicone rubber tubing colonized by incubation with Staphylococcus aureus, Staphylococcus epidermidis, or Klebsiella pneumoniae was used to test the efficacy of various chemicals in vitro. Protocols sterilizing all segments colonized for 24 h (n = 30) were immersion into 50% povidone iodine for 5 and 60 min, 100% povidone iodine for 5, 15, and 60 min, 1.2 x 10(3) ppm chlorine dioxide for 15 and 60 min, and 1.2 x 10(3) ppm chlorine dioxide buffered to pH 5.1 for 60 min. Immersion in up to 2% chlorhexidine, 7.4% formaldehyde, or 6% sodium hypochlorite for up to 60 min failed to sterilize all segments. None of 117 control segments were sterilized. Segments colonized for seven days were sterilized by immersion into 100% povidone iodine for 15 or 60 min. Use of 1.2 x 10(3) ppm chlorine dioxide for 60 min sterilized 97% of segments tested. Lower concentrations and shorter exposure times failed to sterilize all segments. Eighteen silicone rubber catheters, colonized on the outer surface, were all sterilized within 24 h by a chlorine dioxide solution placed in the lumen and diffusing through the wall to kill the bacteria.

Catheterization↗
PubMed1990

The source of circulating catecholamines in forced dived ducks.

Plasma catecholamines have been measured in chronically adrenalectomized (ADX) ducks, in chronically adrenal-denervated ducks (DNX), and in their respective shamoperated controls (SH-adx, SH-dnx) after 3 min forced submergence. The results showed that 100% of the plasma epinephrine (EP) and 70 to 80% of plasma norepinephrine (NE) released during the dive came from the adrenal glands. Only 20 to 30% of plasma NE came from the endings of the autonomic vascular sympathetic nerves which are strongly stimulated during diving. Adrenal catecholamines were released by nerve activation only; nonneural mechanisms did not play any role in their release. The action of adrenal catecholamines on the cardiovascular system during dives was investigated by measuring heart rate and arterial blood pressure in operated and sham-operated ducks. Cardiovascular adjustments, associated with 3 min of forced diving, were not affected by any differences in the levels of plasma catecholamines.

Adrenal Glands↗
PubMed1990

The mortality of first and second generation Irish immigrants in the U.K.

The Irish have generally been ignored in studies of the health needs of ethnic groups in the U.K. despite being the largest immigrant group and having the highest Standardised Mortality Ratio of all first generation immigrants. Using the OPCS Longitudinal Study, the present paper shows that this excess mortality persists into the second generation Irish in the U.K., regardless of the part of Ireland from which their parents originated or whether one or both parents were Irish. The effects of social class, age, sex, year of entry to the U.K. and period of death are explored, and variations with these factors are found to be complex.

Adolescent↗
PubMed1990

Pharmacokinetic screening of o-naphthoquinone 5-lipoxygenase inhibitors.

The o-naphthoquinone derivative, CGS 8515 (I), is a potent inhibitor (IC50, 0.1 microM) of 5-lipoxygenase, but its therapeutic potential is compromised by a short plasma half-life (22 min) and extremely poor oral bioavailability (less than 2%). Poor biopharmaceutical properties of CGS 8515 were attributed to poor aqueous solubility and rapid in vivo hydrolysis of its methyl ester function to an inactive metabolite (IC50, 100 microM). An active amide analogue (II) was synthesized to prevent rapid hydrolysis. While analogue II appeared to be stable in vivo, its plasma half-life was also short (10 min), possibly because of rapid tissue distribution rather than metabolic elimination. Therefore, three potent analogues with increased aqueous solubilities were synthesized and compared with respect to their pharmacokinetic properties. The analogue with the highest aqueous solubility (V) demonstrated a plasma concentration vs time profile with the largest area under the curve (AUC) and the smallest distribution (alpha) phase of all the analogues studied. The percentage AUC of the terminal phase (beta) for three analogs paralleled their aqueous solubilities. The oral bioavailability of V was improved to 27%, compared to 2% for the parent compound, CGS 8515.

Administration, Oral↗
PubMed1990

Origin and structure of benign prostatic hyperplasia.

The development of microradiography of the prostate gland has provided a new approach to investigating the origin and structure of benign hyperplasia. It has demonstrated that benign prostatic hyperplasia is usually microadenomatous in structure, although reticular types do occur. It originates at the lateral boundary of the periurethral muscle in the position of the transitional zone. In contrast, stromal nodules are homogeneous and amorphous in structure and develop at the site of the short straight urethral ducts within the periurethral muscle.

Adolescent↗
PubMed1990

Effects of acute and chronic baroreceptor denervation on diving responses in ducks.

To investigate the effects of barodenervation on the cardiovascular responses to forced submersion, we implanted snares around the aortic nerves innervating the baroreceptors in anesthetized (pentobarbital sodium, 35-45 mg/kg) ducks (Anas platyrhynchos). Snares were withdrawn 1 wk after surgery to effect barodenervation in the absence of complications from surgical trauma or anesthesia. After barodenervation, resting heart rate (HR), hind limb vascular resistance (HLVR), and mean arterial pressure (MAP) all increased, with different time courses, over the 16-day observation period. Bradycardia developed during forced submersion in ducks before and after barodenervation, although this response was reduced for 1-3 days after nerve section. The HR response to diving intensified 4-5 days after denervation, and the level of dive bradycardia at 16 days was similar to that before denervation. End-dive MAP fell further, as a proportion of predive MAP, with time after baroreceptor loss. The absolute level of HLVR reached during diving was unaffected by barodenervation. These results show that diving responses develop in the absence of baroreceptors, but MAP in the dive is not maintained as well in barodenervates as in baroreceptor-intact animals.

Animals↗
PubMed1990

Combat stress disorders and the U.S. Air Force.

Air Force fliers and base personnel have unique spheres of vulnerability to combat stress disorders. A number of factors unique to the Air Force heighten combat stress vulnerability: (1) The passive nature of combat duties, (2) relatively small amounts of combat skills training, (3) absence of service-wide training in arms use, (4) lack of experience with mass casualty situations, (5) family proximity to potential operational areas, and (6) base and personnel immobility. The impact of combat stress disorders for both fliers and nonfliers in the Air Force can be minimized. Prevention, diagnosis, and treatment are discussed.

Aerospace Medicine↗