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J J Alexander

Publications and source records attributed to J J Alexander.

At least 73 records · Page 4Linked to original sources
PubMed1989

The effect of estrogen on low-density lipoprotein binding kinetics in aortic endothelial cells.

The inhibition of atherosclerosis by estrogen has been shown clinically and experimentally, but the mechanism by which this occurs is unknown. Previous studies have shown that estrogen enhances the uptake of low-density lipoprotein (LDL) by bovine aortic endothelial cells (BAEC) while not altering membrane binding at saturating levels of LDL. In this study the effect of estrogen on LDL binding kinetics has been investigated. Computer-assisted Scatchard analysis of binding data suggests a single-site binding model. Estrogen-treated BAEC showed a lower binding affinity (Ka = 2.47 +/- 0.74 E7 M-1) than control cells (1.95 +/- 0.21 E7 M-1) (p = 0.0012). Estrogen-treated cells, however, had a greater binding capacity (Bmax = 1.26 +/- 0.07 E-10M) than control cells (Bmax = 8.49 +/- 0.44 E-11M) (p = 0.0004). The latter was due primarily to a difference in LDL binding at higher concentrations of LDL (greater than 40 micrograms/ml). These findings are consistent with an estrogen-stimulated increase in low-affinity binding of LDL to BAEC, which may not be directly receptor mediated and which appears to enhance the uptake of LDL at higher lipoprotein concentrations. Such alterations in LDL uptake by endothelial cells could influence the formation of atherosclerotic plaque.

Animals↗
PubMed1989

Aorta-vena cava fistula.

In 1831 James Syme described the unusual occurrence of an aortocaval fistula in a 22-year-old man with luetic aortitis. This initial report was followed by illustration of this phenomenon in Rokitanski's Book of Pathologic Anatomy in 1841 and by Ryle's delineation of an aortocaval fistula on a pathologic specimen placed in Guy's Hospital Museum in 1892. The first series of aortocaval fistulas, cited by Rudolf Matas in 1909, consisted of a collection of 20 cases gathered by Boinet 10 years earlier. Several later reports, including those by Reid in 1925 and by Lehman in 1938, failed to add any additional cases. It was not until 1955 that Boffi presented an additional six patients who had this disorder, none of whom survived. Since that time, more than 100 cases of spontaneous aortocaval fistulas have been documented. This increasing experience has resulted in improved understanding and surgical treatment of these large-vessel arteriovenous communications. Nevertheless, lack of awareness and failure of recognition of this problem continue to impede its successful management. In this review we present two additional illustrative cases, summarize the clinical and pathophysiologic features of aortocaval fistulas, and outline present approaches to treatment.

Adult↗
PubMed1988

The relative frequency of subgroup I and II rotaviruses in black infants in South Africa.

Between March 1983 and December 1986, a total of 1571 stool specimens were collected from black South African infants and young children with acute gastroenteritis, and tested for the presence of rotavirus. Monoclonal antibodies against the major inner capsid protein were used in an enzyme linked immunosorbent assay to determine the subgroup specificity of the rotavirus isolates. Subgroup II rotaviruses occurred more frequently than subgroup I isolates (74.4% vs 12.3%), while 13.3% could not be typed and may indicate the presence of a third subgroup. Two of the subgroup I isolates had a long RNA profile (ie, faster moving gene segment 11) typical of the subgroup II human rotaviruses, and a single subgroup II strain had a short RNA profile possibly indicating an in vivo rotavirus reassortant.

Antibodies, Monoclonal↗
PubMed1988

Enteropathogens isolated from children with gastro-enteritis at Ga-Rankuwa Hospital, South Africa.

A prospective 3-year study for enteric pathogens associated with diarrhoea in children was undertaken at Ga-Rankuwa Hospital, South Africa. Rotavirus was the most commonly isolated pathogen (24%), showing a marked seasonal distribution, with an autumn peak in activity. Enterotoxigenic and enteropathogenic Escherichia coli were frequently identified, and Salmonella, Shigella and Campylobacter were also isolated. Cryptosporidium and Giardia lamblia were the most frequently seen parasites. Rotavirus, E. coli, Salmonella and Campylobacter occurred predominantly in children less than 1 year old, whilst Shigella and the parasites were prevalent at all ages.

Animals↗
PubMed1988

Clinical features of acute infantile gastroenteritis associated with human rotavirus subgroups I and II.

During a prospective 3-year study, clinical and epidemiological features of rotavirus gastroenteritis in black infants were investigated. Fever and temperatures exceeding 39 degrees C were more frequent in children shedding subgroup II rotaviruses, whereas vomiting was more pronounced in children with subgroup I infection. Diarrhea, dehydration, duration of illness, and the need for admission to a hospital ward were similar in both groups.

Child, Preschool↗
PubMed1988

The management of localized abdominal aortic dissections.

Aortic dissections limited to the abdominal aorta occur infrequently. We have identified four cases of abdominal aortic dissection and have reviewed these in combination with 43 previously reported cases to identify factors that influence the prognosis and management of this disease. Abdominal aortic dissections are similar to thoracic dissections in their presentation, with acute shearing pain and systolic hypertension occurring commonly. Although the diagnosis may be made by ultrasonography or CT scanning, angiography is the definitive diagnostic study. Factors found to be associated with high mortality include presentation with acute pain (p less than 0.0003), involvement of visceral vessels (p less than 0.02), and rupture (p less than 0.000002). Chronicity appears to be protective (p less than 0.04), although chronic dissections may present acutely. Although prosthetic replacement of the involved aorta is the treatment of choice in most cases, nonoperative management with regular follow-up can be considered in asymptomatic chronic dissections.

Aged↗
PubMed1987

Viruses excreted in neonatal stools.

Faecal specimens from 122 infants in the Neonatal Unit at Ga-Rankuwa Hospital were examined by electron microscopy for the presence of virus. In total 40% of the neonates were excreting virus. Rotavirus was the commonest, found in 33.5% of the infants, with small round viruses (SRVs) found in 12.3% and adenovirus seen in 1 baby. RNA analysis of the rotavirus genome revealed a similar electrophoretype in all specimens. Most of the babies infected with rotavirus were less than 7 days old, and very little excretion occurred after 21 days of age. Only 8% of the babies excreting virus had any clinical signs of infection. Rotavirus infection appears to be endemic and SRV infection common in the Neonatal Unit at Ga-Rankuwa Hospital.

Adenoviruses, Human↗
PubMed1987

Molecular epidemiology of rotavirus in black infants in South Africa.

The molecular epidemiology of rotavirus infections in black infants in Ga-Rankuwa, South Africa, was investigated by polyacrylamide gel electrophoresis. Between 1983 and 1986, 14 different RNA electrophoretic patterns were observed for children with acute gastroenteritis. These electrophoretypes showed a sequential pattern of appearance, with a limited number being present at any one time. In contrast, for neonates only one RNA electrophoretype was detected, which persisted for at least 3 years.

Acute Disease↗
PubMed1986

The use of liposomes to study drug-membrane interactions.

The effects of free and liposome-encapsulated bleomycin and adriamycin on a human hepatocellular carcinoma cell line were studied in vitro. Free and encapsulated bleomycin inhibited cell growth over 24 hours by the same amount, but DNA synthesis was inhibited more by the encapsulated form. Twenty-five per cent of the cell population showed drug resistance to the free drug, whereas this decreased to 17% with encapsulated bleomycin. These results suggest that the cell membrane plays a role in bleomycin resistance, and that cell death is not solely due to inhibition of DNA synthesis. Encapsulated adriamycin inhibited cell growth and DNA synthesis by the same amount or less than the free drug. Possible explanations are that adriamycin exerts its main cytotoxic action by interacting with the cell surface, or that at the low concentrations used, free drug is taken up more efficiently than the encapsulated drug. Liposomes as drug carriers constitute a useful system for studying the basic mechanisms involved in drug action and in particular the role played by cell membranes.

Bleomycin↗
PubMed1986

Rotavirus-associated gastro-enteritis at Ga-Rankuwa Hospital. A pilot study.

During 1982 a pilot study was initiated to investigate the prevalence of rotavirus-associated gastro-enteritis among the infants and young children admitted to the Gastro-enteritis Unit at Ga-Rankuwa Hospital. The seasonal parameters of the area were included in the study. From March to December 1982 rectal swabs were randomly collected from 256 of the more than 3 000 admissions to the unit. The swabs were stored at -20 degrees C until assayed in duplicate by an enzyme-linked immunosorbent assay. Overall 32.8% of the patients tested were found to have a rotavirus-associated illness with a definite seasonal pattern emerging, which is not in accordance with other data published for the black population in the RSA.

Age Factors↗
PubMed1986

Rotavirus-associated gastroenteritis in black infants in South Africa.

From March 1983 to February 1985, rectal swabs were collected from the black infants admitted to the gastroenteritis unit at Ga-Rankuwa Hospital, Pretoria, Republic of South Africa, to investigate the prevalence of rotavirus-associated gastroenteritis. Overall, 23.1% of the patients tested were found to be positive for rotaviral illness; a definite seasonal pattern emerged, showing a marked increase in the number positive during the autumn. Other factors of importance in terms of rotaviral illness included the age distribution of the patients, the presence of vomiting, and duration of illness.

Black People↗
PubMed1986

Repair of a vertebral artery dissection. Case report.

The case is presented of a 38-year-old woman who suffered multiple cerebellar infarctions as a result of emboli from a vertebral artery dissection. Surgical therapy led to a satisfactory recovery. This case emphasizes the importance of an aggressive approach to such lesions.

Adult↗
PubMed1986

New criteria for placement of a prophylactic vena cava filter.

In order to identify patients who, having had an initial pulmonary embolism, are likely to develop recurrent emboli despite adequate anticoagulation therapy, ten patients (group 1) with documented recurrent pulmonary embolism during anticoagulation therapy were compared with 31 patients (group 2) who showed no evidence of recurrent emboli during the treatment period. Risk factors for thromboembolic disease were similar between the two groups. Noninvasive venous studies of the lower extremities, including Doppler venous ultrasound and phleborheography (PRG), were performed upon all patients after the initial embolic event. Of the ten patients in group 1, seven (70 per cent) had clinical signs of deep vein thrombosis (DVT). Doppler studies were positive for eight of the nine patients studied, and PRG studies were positive for eight of eight patients tested. In contrast, of the 31 patients who responded well to medical therapy, one patient (3 per cent) had clinical signs of DVT, three patients (10 per cent) had positive Doppler studies and one patient (3 per cent) had a positive PRG. Combined Doppler and PRG studies were positive in 100 per cent of the patients in group 1 but in only 6 per cent of the patients in group 2 (p less than 0.001). The results of this study suggest that patients having an initial pulmonary embolism and DVT of sufficient extent detected by noninvasive studies may be at an increased risk for recurrent PE despite anticoagulation therapy. Insertion of a vena cava filter should be considered in these patients prior to the second embolic event.

Adult↗
PubMed1985

Hepatitis B virus gene expression in two cell lines, one derived from a natural human infection, the other experimentally infected in vitro.

Hepatitis B virus (HBV) gene expression was investigated in the PLC/PRF/5 human hepatoma cell line and the mouse L-cell line transfected with HBV DNA by modulating the in vitro growth conditions. Both cell lines contain the viral genome integrated into cell chromosomes and both have been shown to produce hepatitis B surface antigen only. Treatment with 5-azacytidine (5-azaC) did not enhance hepatitis B core antigen (HBcAg) synthesis in experimentally transfected mouse L cells. Low levels of hepatitis B e antigen (HBeAg) were detected from the L cells regardless of 5-azaC treatment, and synthesis of HBeAg was dependent on the growth state of the cultures. No HBcAg or HBeAg was detected in PLC/PRF/5 cells with or without 5-azaC treatment. This observation suggests that there is a distinct difference between experimentally transfected cells with HBV and the naturally derived material.

Animals↗