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Biomedical subjects

J H Theis

Publications and source records attributed to J H Theis.

At least 37 records · Page 2Linked to original sources
PubMed1989

Annual cyclicity of gall stone prevalence in deer mice (Peromyscus maniculatus gambelii).

The prevalence of gall stones (100% cholesterol) in a deer mouse (Peromyscus maniculatus) population located in Siskiyou County, California (USA) was studied on a monthly basis from February 1985 through January 1988. During each year we documented a pronounced annual cyclicity with peak prevalence (31 to 53%) during the winter and low prevalence (2 to 3%) during late summer. Gall stone prevalence was not related to sex or age of the animal. The earliest onset of gall stone production and the maximum prevalence achieved were associated with the greatest abundance of deer mice; lower levels of population abundance were associated with later onset of gall stone production and lower peak prevalences. This association of gall stone prevalence with both season and population abundance levels suggests that the causative factor(s) is/are related to the quality and availability of the diet.

Age Factors↗
PubMed1988

Hazards of angioscopic examination: documentation of damage to the arterial intima.

The fiberoptic scope is increasingly used in the coronary and peripheral arteries to quantitate the degree and type of arterial obstructive disease and to inspect the results of procedures such as bypass grafting and laser irradiation of obstructive lesions. Since little is known about this instrument's potential complications, we passed a variety of fiberoptic scopes (1.8 to 3.6 mm outer diameter) in fresh postmortem pig coronary arteries and live monkey and canine peripheral arteries, and observed the intraluminal anatomy through the angioscope. No perforations were created, but ridges rising from the vascular luminal surface, avulsion of the endothelial lining, and small flaps attached at one end to the vessel wall were observed. Histologically, subintimal and medial tears were evident. Inserting large diameter scopes or making frequent passes (10 to 100) in coronary arteries increased intravascular injury. The use of small diameter flexible scopes or infrequent passes (less than 10) in the larger iliac and femoral arteries of live monkeys and dogs resulted in a lower frequency of myointimal sloughing or flap formation. Current fiberoptic scopes are not ideal angioscopes; they have a rigid tip, cannot be steered adequately, and are relatively stiff, resulting in a high probability of intraluminal injury, especially when used in small tortuous arteries. To decrease the risk of such injury, we recommend gentle manipulations while passing the scope and use of the smallest diameter scope possible. We further suggest limited use of the fiberscope, or at least limiting the number of passes in small vessels such as coronary arteries.

Animals↗
PubMed1987

Effects of simultaneous viewing and vaporization of plaques using the steerable, laser-heated metal cap in the atherosclerotic monkey model.

A steerable, fiberoptic catheter coupled to a laser light guide tipped with a metal cap was used. Four monkeys fed an atherogenic diet for 7-8 years were angiographed and were found to have extensive mural plaque in the iliac arteries. Plaque sites in these monkeys were vaporized using the laser-heated metal cap. Energies of 1.5-9 Joules were employed. Application of the energy was tangential of perpendicular to the plaque. Lased sites were examined histologically at 24 hr or at 3 months after treatment. No effect was seen at 1.5 Joules. Three to six Joules tangentially produced a superficial lesion that extended into the tunica intima. Six Joules perpendicularly produced a burn into the tunica adventitia, with damage to the vasavasorum. Nine Joules tangentially produced a burn into the tunica media. Three months after treatment, this lased site showed no stenosis or aneurysm formation.

Animals↗
PubMed1987

Exotic stock of Trypanosoma cruzi (Schizotrypanum) capable of development in and transmission by Triatoma protracta protracta from California: public health implications.

A stock of Trypanosoma cruzi was recovered from a Triatoma dimidiata from Tegucigalpa, Honduras. This stock was shown to be capable of development and transmission by native California Triatoma protracta protracta. Isozyme analysis indicated that this T. cruzi is closely related to the Tehuantepec strain and to a lesser extent the Miles' zymodeme 1 strain. The potential public health significance of development and transmission of exotic stocks of T. cruzi by native reduviids is discussed.

Animals↗
PubMed1985

Agent of Chagas' disease from Honduran vector capable of developing in California insects: implications for cardiologists.

An exotic strain of Trypanosoma cruzi recovered from Triatoma dimidiata from Tegucigalpa, Honduras, was shown by isoenzyme studies to be closely related to the Miles' zymodeme 1 and laboratory reference strain Tehuantepec. It was injected into Swiss random-bred ICR mice. Clean Triatoma protracta nymphs and adults, which had been captured in Winters, California, fed on inoculated mice and were then examined over a 15-month period. Their feces contained multiplying epimastigote and infective trypomastigote forms of T. cruzi. This shows that exotic strains of T. cruzi can develop and survive for long periods in local California vectors. The increasing number of immigrants from Central America who enter California and other states may have public health implications in regard to the introduction of pathogenic strains that are capable of producing cardiomyopathy. Cardiologists who examine patients with cardiomyopathy from Central and South America should rule out Chagas' disease as a cause, since pathogenic T. cruzi strains are present in most Central and South American countries.

Animals↗
PubMed1984

Acute and chronic complications of laser angioplasty: vascular wall damage and formation of aneurysms in the atherosclerotic rabbit.

Acute and chronic vascular responses to laser exposure in atherosclerotic rabbits were studied. In 7 rabbits fed an atherogenic diet for 3 to 5 months before the study to induce aortic atherosclerosis, a flexible quartz fiber, 400 micron core diameter, attached to an argon ion laser was passed anterogradely or retrogradely to the atherosclerotic ascending aorta. The laser was turned on using power intensities of 1 to 2 W for 3 seconds. After laser treatment, the aortas were studied acutely in 3 rabbits and chronically in 4 rabbits after recovery for 1 to 14 days. In 2 rabbits studied acutely, the argon laser produced a vaporized crater within the atherosclerotic plaque at the endothelial surface; however, in 1 there was also vascular damage extending deep into the medial layer. In addition, aortic aneurysm with muscular wall damage occurred in 2 of the 4 animals studied chronically. Thus, vascular complications may arise when catheter laser angioplasty is randomly applied without visualizing specific plaque targets or without using safe dose increments of power intensities and durations of exposure. This study suggests caution in the clinical use of intensive phototherapy to cardiovascular lesions and stresses the need for further understanding of laser vascular consequences before application of laser angioplasty in patients.

Animals↗
PubMed1983

Effects of laser irradiation on human erythrocytes: considerations concerning clinical laser angioplasty.

Recent studies demonstrate the potential use of laser to vaporize human coronary atherosclerotic plaques. The laser energy is transmitted through flexible quartz fiber and discharged intravascularly. Since red blood cells could be exposed to intense heat, we examined effects of laser irradiation on human erythrocytes. Blood was obtained and placed in 5 ethylene diaminetetracidic acid (EDTA) vials for each normal donor. A flexible 400 microns diameter core quartz fiber coupled to an argon-ion laser source was positioned 1 cm above the surface of 1.5 ml blood. Four vials were exposed to 5 W laser beam for 5, 10, 15, or 20 s; the remaining vial was left untreated. Packed cell volume fell primarily during the first 5 s of laser exposure (p less than 0.01) and plateaued beyond 5 s. Plasma hemoglobin (Hgb) rose progressively with each increased duration of exposure (p less than 0.01). This study indicates that lysis of erythrocytes occurs in cells exposed directly to the laser beam. However, beyond the direct beam, damage to red cell membrane took place as evident by progressive Hgb leakage into plasma despite no further cell lysis. These observations require consideration during clinical laser angioplasty.

Erythrocyte Indices↗
PubMed1982

Prevalence of heartworm (Dirofilaria immitis Leidy) in coyotes from five northern California counties.

Prevalence rates of heartworm in coyotes was estimated for five northern California counties by examining hearts of coyotes obtained from federal or private trappers. Prevalence rates range from 8.3-27.3%, but the proportion of infected coyotes can vary between two regions of the same county. In general, it seems that higher infection rates are found in the foothill regions of the Coastal Range and Sierra Nevada, decreasing towards the floor of the Sacramento Valley as well as at higher elevations. The use of coyotes as sentinel animals for detecting natural foci of transmission is postulated.

Animals↗
PubMed1980

Viral agents recovered from Ornithodoros coriaceus, a vector of epizootic bovine abortion.

Two unidentified viral isolates from the tick, Ornithodoros coriaceus, the probable vector of the causative agent of epizootic bovine abortion, did not cause any untoward reactions in pregnant heifers which were experimentally inoculated or which were exposed to bites of O coriaceus that had been infected with cultures of the two isolates. Seemingly, neither viral isolate is involved in the cause of epizootic bovine abortion.

Abortion, Veterinary↗
PubMed1980

Preliminary studies on transmission of Chlamydia to cattle by ticks (Ornithodoros coriaceus).

Preliminary findings indicate that Ornithodoros coriaceus ticks can harbor Chlamydia for long periods and are able to transmit the agent to cattle. Field-collected O coriaceus ticks, which were infected experimentally with a bovine chlamydial agent from an aborted fetus, transmitted the agent 25 and 48 days later to three pregnant heifers. Two of these heifers aborted and the third delivered a term calf. The control heifer also aborted after intradermal (simulated tick) exposure. Also, a chlamydial agent was isolated from field-collected O coriaceus ticks in an epizootic bovine abortion (EBA)-enzootic area that were held for at least 6 months. In the same enzootic area, a chlamydial agent was isolated from a prematurely delivered calf during a severe EBA outbreak. Seemingly, this species is a cause, if not the cause, of EBA.

Abortion, Veterinary↗
PubMed1979

Diocytophymatid larval nematode in a subcutaneous nodule from man in California.

A nematode in a subcutaneous nodule excised from the chest of a man in central California is described and identified as a third-stage larval dioctophymatid, probably Dioctophyma renale, though a Eustrongylides species could not be excluded. In all well-documented previously reported cases of D. renale infection in man, none of which was from North America, adult worms were discovered in the kidney at autopsy (5 cases), or were observed migrating or being expelled through the urethra (6 cases), discharged through the skin over an abscessed kidney (1 case), or detected by finding eggs in the urine (1 case).

Adult↗
PubMed1979

Experimental congenital infection of Toxoplasma gondii in Macaca arctoides.

Congenital toxoplasmosis was studied in Macaca arctoides as a model for primates. Time-mated female monkeys were assigned to 5 experimental groups and inoculated with 4 different strains of Toxoplasma gondii before pregnancy and during various stages of gestation. All monkeys showed a rise in indirect hemagglutination antibody (IHA) titers following infection, and some had demonstrable parasitemia. Of the 23 progeny, 2 were stillbirths and 2 died soon after birth, but only the one neonate born of a mother inoculated intrauterally succumbed to acute toxoplasmosis. No physical anomalies were observed in any of the progeny. The toxoplasms organism was not isolated from any of the placentas obtained nor from the cord blood. None of the tissues from the stillborn or infant monkeys that died were positive for toxoplasmosis by mouse inoculation. The live progeny were usually born with high IHA antibody titers which were usually soon lost, indicating presence of passively acquired maternal antibody. However, 2 babies, born of mothers infected with tissue cysts on day 79 and 149 of gestation, maintained moderate to high titers for about 8 and 19 months respectively, indicating that an active infection had taken place but no clinical disease was detected. Data obtained suggest that although certain developmental stages of the toxoplasma organism and of the fetus may favor the occurrence of congenital infection, very little neonatal disease results in this primate model.

Animals↗