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Biomedical subjects

B Davidson

Publications and source records attributed to B Davidson.

At least 127 records · Page 7Linked to original sources
PubMed1992

The incidence of myopia in the Israel Air Force rated population: a 10-year prospective study.

It is important to define the risk in pilots of becoming myopic in order to determine the need for yearly screening, and to predict pilot eligibility in environments where the use of corrective lenses may present problems. We conducted a prospective study of 1400 air force personnel followed for 10 years, who could be divided into three major groups; those with 20/20 vision in both eyes, those with 20/25 in one eye only and whose vision was 20/20 using both eyes together, and those who were accepted despite the fact that they required corrective lenses. Over the 10-year period, 23.1% of those with 20/25 visual acuity in one eye needed corrective lenses, significantly more than the 7.4% observed in those with 20/20 vision in both eyes (relative risk 3.1, 95% confidence interval 2.2-4.3, p less than 0.0000). The prevalence of corrective lenses increased until age 26. We conclude that 7.4% of pilots will become myopic over a 10-year period if accepted with 20/20 vision in both eyes. The risk, however, is much higher in those with incipient growth myopia starting in one eye at entry. Therefore, the annual screening of visual acuity in air force personnel is essential.

Adolescent↗
PubMed1991

Identification of male-factor semen samples prior to insemination and in vitro fertilization.

Semen analyses carried out as part of the clinical in vitro fertilization or intrauterine insemination protocols provide important information that determine the type of clinical treatment of the male partner and the sperm processing method. It is postulated that the sperm of male-factor patients cannot survive hypoosmotic stress conditions because of defective sperm membrane function. To test this, 0.1 ml of semen from each of 102 patients was placed in 1.0 ml of 150 mosmol/liter eosin citrate fructose solution and incubated for 30 min at 37 degrees C. The percentage viability of the sperm cells was then determined. The results indicated that patients with two or more abnormal semen parameters had a significantly lower percentage viability while in the hypoosmotic solution (40.6 +/- 4.7%), in contrast to non-male-factor patients (69.0 +/- 1.6%). Donor sperm (N = 32) serving as controls (73.3 +/- 2.1%) had a viability in hypoosmotic solution similar to that of non-male-factor patients. The data suggest that sperm of male-factor patients are less able to survive the hypoosmotic stress conditions as shown by the percentage viability in hypoosmotic solution and emphasize the importance of using less stressful sperm processing methods for in vitro fertilization or insemination in these patients.

Cell Membrane↗
PubMed1991

Surgical emergencies in liver disease.

In this chapter the surgical management of bleeding oesophageal varices, ruptured hepatocellular carcinoma and fulminant liver failure have been discussed. Bleeding oesophageal varices can usually be successfully treated with vasopressin, balloon tamponade and injection sclerotherapy. Emergency surgery should be considered if two courses of injection sclerotherapy have failed to achieve haemostasis. Stapled oesophageal transection and portosystemic shunting are currently the two most popular procedures. The former is associated with a lower morbidity and mortality as well as a lower incidence of subsequent encephalopathy. Ruptured hepatocellular carcinomas are usually associated with liver cirrhosis and impaired liver function. Selective coeliac axis cannulation followed by embolization of the hepatic artery branches supplying the tumour is an effective method of achieving haemostasis and is associated with a lower morbidity and mortality than emergency hepatic artery ligation or liver resection. If haemostasis is achieved by embolization the patient may subsequently be assessed for an elective resection of the tumour. Fulminant liver failure may be managed by supportive medical therapy or orthotopic liver transplantation. Patients whose liver failure is graded as mild (grade I) should be treated by medical therapy, whereas those with severe liver damage (grades III and IV) should be assessed for transplantation. Accurate monitoring of the patient's clinical progress and prognostic indicators are vital in deciding whether conservative treatment should be continued or liver transplantation performed.

Carcinoma, Hepatocellular↗
PubMed1991

Cardiovascular adaptations in Andean natives after 6 wk of exposure to sea level.

Six male Quechua Indians (34.0 +/- 1.1 yr, 159.5 +/- 2.1 cm, 60.5 +/- 1.6 kg), life-long residents of La Raya, Peru (4,350-m altitude with an average barometric pressure of 460 Torr), were studied using noninvasive methods to determine the structural and functional changes in the cardiovascular system in response to a 6-wk deacclimation period at sea level. Cardiac output, stroke volume, and left ventricular ejection fractions were determined using radionuclide angiographic techniques at rest and during exercise on a cycle ergometer at 40, 60, and 90% of a previously determined maximal O2 consumption. Subjects at rest were subjected to two-dimensional and M-mode echocardiograms and a standard 12-lead electrocardiogram. Hemoglobin and hematocrit were measured on arrival at sea level by use of a Coulter Stacker S+ analyzer. After a 6-wk deacclimation period, all variables were remeasured using the identical methodology. Hemoglobin values decreased significantly over the deacclimation period (15.7 +/- 1.1 to 13.5 +/- 1.2 g/dl; P less than 0.01). The results indicate that the removal of these high-altitude-adapted natives from 4,300 m to sea level for 6 wk results in only minor changes to the cardiac structure and function as measured by these noninvasive techniques.

Acclimatization↗
PubMed1991

Hepatolithiasis associated with anomalous biliary anatomy and a vascular compression. Hepatolithiasis and anomalous anatomy.

Biliary tract abnormalities occur in about one of every three people, usually being minor and of no clinical significance. Major abnormalities, however, may present in an unusual manner and provide a major hazard to the unsuspecting surgeon. A patient presenting with cholangitis without jaundice or abnormal liver function tests is reported. Endoscopic retrograde cholangiography failed to demonstrate any bile ducts in the right postero-lateral segments of the liver, the "naked segment sign". A percutaneous transhepatic cholangiogram demonstrated a stricture obstructing the right posterior segmental hepatic duct with hepatolithiasis above the stricture. At operation an anomalous vessel was found at the site of the stricture. This case highlights the unusual way in which biliary tract anomalies may present and the importance of adequate pre-operative investigation.

Aged↗
PubMed1991

Controversy in the management of cholangitis secondary to hydatid daughter cysts.

A 36 year old Cypriot woman, resident in the U.K. since the age of three years, presented with pyrexia, jaundice and upper abdominal pain. On ultrasound examination the biliary tree was dilated, contained sludge and a cystic lesion was present in the liver. An endoscopic cholangiogram showed multiple filling defects in the bile duct which were not felt to be removable endoscopically and a nasobiliary drain was therefore inserted. On resolution of the cholangitis with drainage and antibiotics a laparotomy was performed. The right lobe of the liver was largely replaced by a multiloculated cyst and the bile duct contained multiple hydatid daughter cysts. A right hepatectomy was performed with t-tube drainage of the evacuated bile duct. She made an uneventful recovery and has had no problems on subsequent follow up. Histology confirmed an intrabiliary rupture of a hydatid liver cyst. Cholangitis secondary to daughter cysts is a rare but recognised complication of hydatid liver cysts. Management of hydatid liver cysts by formal resection is controversial but may be preferable in this situation.

Adult↗
PubMed1990

Dose-limiting toxicity of rifabutin in AIDS-related complex: syndrome of arthralgia/arthritis.

We studied the tolerance of humans to rifabutin, a rifamycin with antimycobacterial and in vitro anti-HIV activity. Sixteen subjects with AIDS-related complex were treated for 4-66 weeks with stepwise increasing oral doses of rifabutin from 300 to 2400 mg/day. The highest dose attained was twice that previously reported for humans. Serum and cerebrospinal fluid levels of drug were detected by high-pressure liquid chromatography. A reversible syndrome of arthritis/arthralgia, not previously described, was seen in most (nine out of 10) of those given doses exceeding 1050 mg/day. Uveitis and aphthous stomatitis developed at doses of approximately 1800 mg in two of those with joint manifestations. Typical manifestations of Reiter's syndrome were not seen in any patient. An orange-tan skin pigmentation was almost universal. Other toxicities resembled those previously associated with rifampin. Serum levels did not approach those found to inhibit HIV significantly in vitro. No consistent antiviral or immunological effects were observed; even at the highest doses, rifabutin did not appear to inhibit cellular immunity. Rifabutin was well tolerated at daily doses blow 1 g.

AIDS-Related Complex↗
PubMed1990

Ethical reasoning associated with the feeding of terminally ill elderly cancer patients. An international perspective.

An international nursing research study examined the ethical decision-making of "good and experienced" registered nurses in eight countries. The subjects were asked about their decision to feed or not to feed a hypothetical terminally ill, mentally alert, elderly cancer patient who refuses to eat. Cultural variations were demonstrated in the decisions as well as differences in ethical justification. The majority of nurses who would not feed appeared to use the principle of autonomy, whereas nurses who would feed the patient used beneficence as justification. Conditions under which nurses would change their decision to either feed or not feed the patient against her will included doctor's orders and lack of peer support for the decision. The majority of nurses clearly experienced a dilemma.

Adult↗
PubMed1989

Efficacy of rifabutin in the treatment of AIDS-related complex.

We performed a phase 1-2 antiviral dose escalation trial of rifabutin, a rifamycin antibiotic with anti-HIV-1 activity in vitro. We followed 16 men with AIDS-related complex (ARC) for a mean duration of 29 weeks; the maximum toxicity-limited dose of rifabutin was 2400 mg/day, which was achieved in two patients. There was some evidence of anti-HIV-1 activity in two patients, one of whom had an improvement in immune status, but 11 of the 16 patients showed a deterioration in either virologic or immunologic status. The majority of the patients under study remained clinically stable during the trial, but there was clinical deterioration in the three who entered with CD4 cell counts of less than 100 x 10(6)/l. On the basis of this trial, rifabutin as a single antiviral agent does not appear to be beneficial to ARC patients.

AIDS-Related Complex↗
PubMed1988

Essential fatty acids modulate apomorphine activity at dopamine receptors in cat caudate slices.

We have used a classical neurotransmitter release model to investigate the effect of dietary polyenoic fatty acids on the sensitivity of the presynaptic dopamine autoreceptor in slices of cat caudate nucleus. Maximum inhibition of [3H]dopamine release was seen only in animals fed a diet containing post delta-6-desaturation fatty acids of both the w3 and w6 series. The removal of either or both groups of fatty acids resulted in attenuation of sensitivity of the autoreceptor to apomorphine. We propose that a balance of w3 and w6 fatty acids is required to maintain normal dopaminergic function in the cat caudate nucleus.

Animals↗
PubMed1988

Leiomyomas of the duodenum.

Leiomyoma is a neoplasm of smooth muscle relatively common in the stomach, but very rare in the duodenal location. Symptoms are gastrointestinal bleeding or abdominal pain resembling peptic disease. Three cases of duodenal leiomyomas are described, and the importance of endoscopy is emphasized as a diagnostic tool. Surgical resection of the tumor is the recommended therapeutic procedure, and the difficulty in deciding at the pathological examination whether the leiomyoma is benign or malignant demands prompt follow-up of patients after surgery.

Aged↗
PubMed1988

Comparison of complications following frontal sinus fractures managed with exploration with or without obliteration over 10 years.

Two hundred twelve patients were treated for facial or skull trauma at the West Virginia University Hospital between the years 1977 and 1987. Sixty-six of these patients had frontal sinus or nasofrontal duct trauma. Follow-up information was obtained on 64 of these patients through clinic visits, chart review, questionnaires to patients and physicians, and telephone calls to the patients. Follow-up greater than 1 year was obtained on 52 patients. Sixty-four patients were managed either with a frontal sinus obliteration or with an open exploratory procedure. The incidence of complications occurring in the past 10 years after each of these procedures is compared. Because the indications for each procedure vary somewhat, data is presented on fracture etiology, associated injuries, specific fracture location, fracture displacement, severity of injury, and associated cerebrospinal fluid leaks.

Adolescent↗
PubMed1987

Porphyria--the UCT experience.

Several forms of porphyria are commonly seen in South Africa. Much of the knowledge accumulated in this field has been due to the meticulous research of Professor Lennox Eales and his colleagues at the University of Cape Town. Professor Eales headed the Porphyria Research Group, founded by the CSIR in 1957 and upgraded to a Unit by the MRC in 1979, until he retired in 1983. Since then porphyria research at UCT has continued within the MRC Liver Research Centre. We present here a description of those forms of porphyria commonly seen in South Africa, based in part on recent work carried out at UCT and in part on the work of Lennox Eales, to whom we dedicate this article.

Acute Disease↗
PubMed1987

The consequences of early marriage on marital dissolution.

This study is concerned with the negative effects of early marriage on marital stability. "The focus on this paper is an analysis of a path model which includes the estimated effects of antecedents of early marriage, early marriage and education on the probability of divorce. Findings using the [U.S.] General Social Surveys support research that suggests that early marriage is the most important varialbe influencing divorce. Further, little influence of the early marriage measure through education was found."

Americas↗