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Biomedical subjects

H Alexander

Publications and source records attributed to H Alexander.

At least 109 records · Page 6Linked to original sources
PubMed1991

Microcapsules through polymer complexation. II. By complex coacervation of polymers containing a low charge density.

Relationships between ionizable group content, structure and molecular weight, solubility and solution behaviour, and the efficacy of ionic complex formation through complex coacervation, have been established for a range of sparingly soluble synthetic weak polyelectrolyte polymers with low charge content, based on hydroxyalkyl methacrylates. Selected polymers containing methacrylic acid (acidic) and dimethylaminoethyl methacrylate (basic) functionality show promise as capsule-forming pairs for the entrapment of mammalian cells. The solubility of basic polymers and their ability to form microcapsules with structural integrity is enhanced through quaternization of the N-methyl functionality to the quaternary ammonium group. The survival of guinea-pig erythrocytes encapsulated for 4 d in this promising system was shown by the Drabkin's test to be about 41% of the control sample.

Animals↗
PubMed1991

Monkey model of severe volume-controlled hemorrhagic shock with resuscitation to outcome.

Seventeen cynomolgus monkeys under N2O analgesia and sedation were subjected to severe volume-controlled hemorrhagic shock (shed blood volume of 21 or 27 ml/kg). In 12 monkeys, resuscitation was started after increasing periods of hemorrhagic shock from 30 min to 5 h. In five additional monkeys, volume-controlled hemorrhage was modified at hemorrhagic shock 30 min to control MAP at 30 mmHg: resuscitation was started at hemorrhagic shock of 2 h. A clinically relevant resuscitation protocol consisted of a field phase from 0 to 6 h (lactated Ringer's solution, spontaneous breathing), and a hospital intensive care phase from 6 h to 48 h (blood, lactated Ringer's solution to mean arterial pressure (MAP) greater than or equal to 70 mmHg, controlled ventilation, advanced life support). Fifteen of the 17 monkeys survived. After outcome evaluation at 4 or 7 days, the eight monkeys with "moderate insult" had only transient functional impairment. Of the nine with "severe insult," three showed signs of moderate transient non-oliguric renal failure. Eight of the 12 monkeys studied morphologically showed scattered liver cell damage. None of the monkeys developed pulmonary dysfunction or functional or morphologic evidence of cerebral damage. This study establishes a new hemorrhagic shock-resuscitation model simulating field-to-hospital life support. Severe hemorrhagic shock with MAP 30-40 mmHg for 90-120 min (without trauma or sepsis) can lead to complete functional recovery after transient malfunction of liver and kidneys.

Animals↗
PubMed1991

Does the occupational structure of the Hunter Region explain the high rates of ischaemic heart disease among its men?

To compare rates of ischaemic heart disease (IHD) among men in occupation groups defined by the new Australian Standard Classification of Occupations (ASCO) and to investigate whether their high mortality rates from IHD in the Hunter Region of New South Wales (NSW) could be explained by its occupational structure, we used official death records and data from the World Health Organization MONICA Project conducted in Newcastle. The study population consisted of men aged 25 to 64 years in NSW and in the Hunter Region for whom occupational information was available. For deaths from IHD between 1984 and 1988 in NSW, indirectly standardised mortality and morbidity ratios (SMRs) were: significantly low for professionals, 66 (95% confidence interval (CI) 60-71) and managers and administrators, 79 (95% CI 74-83); intermediate for paraprofessionals (92), clerks (94) and salesmen and personal service workers (97); and significantly high for tradesmen, 113 (95% CI 107-118), labourers and related workers, 118 (95% CI 113-124) and plant and machine operators and drivers, 125 (95% CI 118-133). Broadly similar patterns were found for IHD deaths and for fatal and nonfatal myocardial infarction in the Hunter Region. When occupation- and age-specific mortality rates from IHD were used to calculate SMRs for the Hunter Region, SMRs for all ASCO groups except paraprofessionals were over 100. Mortality rates for occupational groups classified by ASCO were consistent with well-established differences associated with socioeconomic status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Who eats what? A comparison of dietary patterns among men and women in different occupational groups.

Dietary data were obtained during a community-based study of risk factors for heart disease in 1983. Results were compared for men and women in broadly defined socioeconomic groups based on occupation and education. People in higher status occupation groups and with more education, and women more than men, had food consumption patterns more consistent with current health promotion messages. For example, they reported eating more wholemeal or brown bread and more fresh fruit and vegetables, drinking more skim or low-fat milk, eating fewer eggs and having less sugar in hot drinks or on cereals. There was some evidence, however, of an interplay of influences of cost and health awareness. For example, retired men were less likely than employed men to eat butter, cream, fresh fruit and vegetables, while men in the upper socioeconomic groups reported relatively higher consumption of butter and cream. The results emphasise the need for a range of strategies aimed at specific subgroups in order to improve national dietary patterns in Australia.

Adult↗
PubMed1991

Comparison of bovine collagen xenografts to autografts in the rabbit.

The use of bovine tendon as a xenograft material in humans is attractive because of its ready availability and favorable mechanical characteristics. Previous research has shown that the fibroblasts and some extracellular proteoglycans and glycoproteins, not the collagen matrix itself, in bovine tendon are primarily responsible for its antigenicity. Various attempts have been made to decrease the antigenicity of these grafts. A chloroform/methanol (CM) extraction procedure has been developed that selectively removes the fibroblasts from bovine tendon without destroying the collagen matrix. The mechanical, immunologic, and local host tissue responses to these grafts were compared to autografts and to untreated and glutaraldehyde-treated bovine tendon xenografts. The humoral immune response to a purified bovine Type I collagen product was also studied. The central two-thirds of a rabbit Achilles tendon were replaced with a reversed autograft or an experimental graft. Histologic examination of one- and two- week specimens showed an acute inflammatory response to all grafts. Untreated grafts stimulated a severe inflammatory response and were almost completely resorbed by two weeks. Glutaraldehyde-treated grafts were encapsulated. Cellular repopulation was minimal and inflammatory response was more persistent than in the autograft and CM groups. Inflammatory response to CM-treated grafts was similar to that of autografts. The CM grafts repopulated rapidly with host cells. The mechanical strength of CM grafts was equal to autograft controls at 12 weeks. The mechanical strength of untreated and glutaraldehyde-treated grafts was significantly lower. Measurement of the humoral immune response to these grafts was conducted in an independent group of animals using an enzyme-linked immunosorbent assay. A significant antibody response to untreated, glutaraldehyde-fixed, and CM-treated grafts was detected at 30 days. Antibody titers to glutaraldehyde-fixed and untreated grafts remained elevated at 60 and 90 days. In the CM group, antibody titers decreased to the level of autograft controls by 90 days. No significant antibody response was detected toward purified bovine Type I collagen.

Achilles Tendon↗
PubMed1990

A biomechanical study of tendon adhesion reduction using a biodegradable barrier in a rabbit model.

Adhesion formation associated with tendon surgery is a widespread problem in which a healing tendon becomes adherent via scar tissue to surrounding structures such as bone, muscle, skin, tendon sheath, or other tendons. A model is described in which adhesions were generated reproducibly between the plantaris and Achilles tendons of the rabbit using a partial tenotomy, a Bunnel suture, and immobilization. Using this model, the effect of an absorbable barrier, INTERCEED (TC7), on adhesion formation was investigated. This material, which is a fabric comprised of oxidized regenerated cellulose, was found to diminish significantly the extent and severity of intertendinous adhesions, assessed both mechanically and histologically. No evidence of a foreign body reaction was observed.

Animals↗
PubMed1990

A new canine model to evaluate the biological response of intramedullary bone to implant materials and surfaces.

A new canine model utilizing an implantable chamber with multiple bone ingrowth channels has been used to study the response of intramedullary bone to various implant materials and surfaces. The first group of dogs received implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated (HA-coated) titanium alloy, and polyethylene. A pattern of early initial bone ingrowth by 2 weeks, becoming maximal at 6 to 12 weeks with remodeling to a more mature lamellar bone, and later resorption by 24 weeks was seen for all test groups, with fibrous tissue interfaces covering the smooth test coupons at all time points. Significantly increased bone ingrowth in the sputter-HA coated group was found only at 6 weeks. The second group of dogs received implants with channels lined by surface-roughened coupons of either titanium or plasma-HA-coated titanium, half of which were also packed with a crystalline-HA grouting at the time of surgery. At both 6 and 12 weeks, bone ingrowth was greatly enhanced by the presence of the plasma-HA coating or the crystalline-HA grouting as compared to the uncoated titanium channels. Histologically, bone was seen to bond directly to the plasma-HA coating and the crystalline-HA grouting. A thin fibrous tissue layer was noted between bone and the titanium in most areas, but evidence of direct bone contact to the metal surface was seen. Mechanical testing in tension of intact coupon-bone-coupon units revealed significant strength of the bone-plasma-HA bond, with failure initiating at the metal-HA interface with forces of 15.3 N at 6 weeks, increasing to 44.8 N at 12 weeks. Plasma-HA-lined channels with crystalline-HA packing required similar forces for failure. No significant adhesion strength was noted for the titanium channels at 6 weeks, and only the crystalline-HA-filled channels displayed measurable strength of the bone-titanium interface at 12 weeks, with a force of 9 N needed for failure.

Animals↗
PubMed1990

[Anesthesia for laparoscopy in sterile patients].

During 5 years 382 laparoscopies were carried through in female patients with sterility in different kinds of anaesthesia (Intubation anaesthesia, spinal anaesthesia, and i.v. anaesthesia). We found the most advantageous results in the cases of i.v. anaesthesia with Ketamin and Diazepam.

Adult↗
PubMed1990

[Chlamydia infection in gynecology].

The frequency of chlamydial infections was investigated by means of the McCoy culture technique and a serological procedure using the microimmunofluorescence test in female outpatients showing suspect symptoms; in patients suffering from acute salpingitis, and in women with involuntary infertility. In 18.6% of 290 subjects of the first group, chlamydiae were isolated from cultures. Of 26 patients with acute salpingitis, Chlamydia trachomatis could be detected in 10. The high frequency of positive serological tests suggests chlamydial infection to constitute an important etiological factor in female infertility and extrauterine pregnancies.

Adolescent↗
PubMed1990

A new canine model to evaluate the biological effects of implant materials and surface coatings on intramedullary bone ingrowth.

A new animal model for examining the intramedullary bone response to various implant materials and surfaces is presented, utilizing an implantable chamber with multiple bone ingrowth channels placed through a cortical defect in the lateral aspect of the distal femur. Twelve adult mongrel dogs received bilateral implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated titanium alloy, and UHMW polyethylene. A pattern was detected for all test groups of early initial bone ingrowth by two weeks, which became maximal at six to twelve weeks, followed by remodelling to a more mature lamellar bone and later resorption by 24 weeks, with fibrous tissue interfaces covering the smooth test coupons of all groups at all times. Significantly increased bone ingrowth in the sputter-HA coated group was found only at six weeks.

Animals↗
PubMed1989

New monkey model of severe-volume controlled hemorrhagic shock.

Three series of experiments were conducted to develop a model of volume-controlled severe hemorrhagic shock in the unanesthetized analgesic cynomolgus monkey. This report concerns the insult without resuscitation. In Series I, seven monkeys were sedated with 75% N2O/25% O2, bled 40% of their measured blood volume over 20 min and observed until death. Mean arterial pressure (MAP) decreased to 21 +/- 6 mmHg, spontaneously increased to 46 +/- 5 mmHg, then gradually decreased to pulselessness at 146 +/- 42 min (range 101-213). Hemodynamic variables, lactate, base excess, electroencephalogram and sagittal sinus PO2 followed the same biphasic pattern. In Series II, eight monkeys were bled 27 ml/kg (43% of estimated blood volume) over 20 min under the same N2O analgesia and with similar responses as in Series I. In Series III 26 monkeys were bled 27 ml/kg over 20 min (time zero) as in Series II. Three developed apnea and pulselessness at end of hemorrhage. In 23 the shock period was prolonged for testing resuscitation therapies. Starting at 0 + 30 min, MAP was controlled with minute blood volume adjustments at 30 mmHg until 0 + 2 h. Three died due to inaccurate (preventable) MAP adjustments. At MAP 30 mmHg, all animals lost consciousness, EEG activity decreased, and brain stem reflexes disappeared. The "volume-pressure controlled" hemorrhagic shock model of Series III retains the initial natural response to bleeding, simulates the clinical picture of severe prolonged shock without anesthesia, and represents a more controllable insult than volume controlled hemorrhage alone.

Animals↗
PubMed1989

[Genital chlamydia infections and extrauterine pregnancy].

Serum samples of 217 patients with ectopic pregnancy (e.p.) and of 152 women with intrauterine pregnancy (i.u.p.) were examined for their antibody content to chlamydia trachomatis by means of the indirect immunofluorescence technique. In 81% of the sera of patients with e.p., antibody could be detected, while patients with i.u.p. revealed antibody in 39%. Titres greater than or equal to 1:128 were found in 49% (e.p.) and in only 11% (i.u.p.) respectively; so they possess a high diagnostic value. These results show significant differences in the behaviour of antibodies in both groups of patients and are illustrated in 2 charts. Anamnestic data showed 54% of the patients with e.p. (i.e. adnexitis 23%, gonorrhea 12.3%, previous e.p. 18.4%); the mean age was 29 years. Affected tubes may lose their physiological function, possibly resulting in an ectopic pregnancy. The level of antibody in the serum remains stabile for many years, this enables a retrospective diagnosis of chlamydial infections. An early diagnosis and treatment, including the partners, represent the best way for prevention of complications.

Adult↗