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Biomedical subjects

G L Jackson

Publications and source records attributed to G L Jackson.

At least 109 records · Page 6Linked to original sources
PubMed1981

Radionuclide imaging of experimental myocarditis.

The ability of 67Ga citrate and 99mTc pyrophosphate cardiac imaging to detect myocarditis was assessed in an experimental rabbit model. Twenty-three rabbits were imaged approximately 72 hours after infusion of i.v. norepinephrine. Diffuse cardiac uptake was found in 13 of 15 rabbits scanned with 67Ga. Tissue distribution studies documented significant myocardial uptake of 67Ga in those with positive scans. Precordial imaging and tissue distribution studies revealed no cardiac uptake in the eight rabbits scanned with 99mTc. Histologic examination of all 23 hearts revealed qualitatively similar, typical lesions of myocarditis. This study suggests that cardiac imaging with 67Ga may be useful in the detection of myocarditis.

Animals↗
PubMed1980

Thallium-scan myocardial defects and echocardiographic abnormalities in patients with sarcoidosis without clinical cardiac dysfunction. An analysis of 44 patients.

Sarcoidosis of the myocardium, an illness occurring predominantly in young adults, frequently becomes clinically apparent when the disease is far advanced. Since the thallium myocardial perfusion scan (TMPS) is known to be capable of detecting granulomas, it seemed to be promising as a noninvasive means of screening for this complication of sarcoidosis. We, therefore, examined 44 consecutive patients with sarcoidosis, none of whom had clinical evidence of heart disease, utilizing TMPS, echocardiography, electrocardiography, systolic time interval ratios (PEP-LVET) and 24-hour Holter monitoring. TMPS disclosed left ventricular defects in 14 patients (32 per cent) and abnormalities of the right ventricle in an additional four patients. Left ventricular abnormalities on the TMPS were associated with echocardiographic evidence of left ventricular dysfunction (widened mitral E point septal separation) but not with abnormalities on Holter monitoring or electrocardiograms. Systolic time interval ratios were insensitive but highly specific for the presence of abnormalities on the TMPS. We conclude that the TMPS frequently discloses abnormalities in sarcoidosis, which may be a reflection of its sensitivity in this setting.

Adult↗
PubMed1980

Diagnostic techniques in cardiovascular nuclear medicine.

"Hot-spot" and "cold-spot" myocardial imaging and first-pass and gated equilibrium blood pool studies are the most common cardiovascular nuclear medicine procedures. The data provided by these tests may be vitally important in making decisions, primarily in patients with suspected coronary artery disease. These studies are best performed where there is close coordination between the cardiovascular specialist and the nuclear medicine department. We believe that only a minority of patients with heart disease require these tests, but for those in whom they are indicated, the information obtained can be invaluable.

Coronary Disease↗
PubMed1980

Cryptorchid rhesus macaques: long term studies on changes in gonadotropins and gonadal steroids.

We studied the relationship of testosterone (T), dihydrotestosterone (DHT), and 27 beta-estradiol (E2) to FSH and LH in the systemic circulation of six rhesus macaques with surgically induced cryptorchidism at selected times over 420 days. We measured these hormones by RIA and compared their concentrations with those of four sham-operated controls. Midway through the experimental procedure the animals were electroejaculated, and on day 425 the testes were removed and analyzed histologically. The cryptorchid monkeys did not have sperm in their ejaculates, and treatment adversely affected spermatogenesis. For the first 30 days after treatment none of the hormones differed significantly between cryptorchid monkeys and controls. Gonadotropins in three castrated males, however, gradually rose to postcastration levels within approximately 2 weeks post operation. After castration, all three steroids declined significantly within 24 h. Beginning on days 60, 150, 215, 320, and 420 post operation the animals were bled for 5 days on a diurnal regimen. The steroids as well as LH concentrations varied diurnally. The concentration of FSH never showed diurnal variation in any of the groups at any of the periods studied. Concentrations of T and LH did not differ significantly between control and cryptorchid groups at any time. With longer time periods (beginning 215 days after cryptorchidism had been induced), DHT in cryptorchid monkeys was significantly higher than in controls (P < 0.01). Although E2 was significantly lower in cryptorchid monkeys on days 60 and 150 post operation, this difference disappeared with time. Changes in steroid concentrations were not associated with the elevations in FSH that occurred in cryptorchid monkeys by days 60 and 420. Therefore, we assumed that they were independent phenomena. Significant FSH elevations in cryptorchid monkeys occurred only in the fall of the year. Testicular homogenates from cryptorchid and control monkeys produced similar quantities of T, DHT, and androstenedione in vitro. Very little E2 or estrone was found. Although significant amounts of progesterone were quantified in the incubation media of control testes, little or no progesterone was found in media from cryptorchid testes. Similar results were obtained when these steroids were measured in plasma collected from the testicular veins. In testicular venous plasma, 20 alpha-dihydroprogesterone concentrations were not elevated after cryptorchidism. These data suggest that there is similar negative feedback control of gonadotropins in crytorchid and control rhesus monkeys. The absence of dramatic differences in systemic concentrations of FSH between the two groups suggests that the seminiferous tubule does not play a major role in the negative feedback control of gonadotropins in this species or that the tubular component of this control system is not perturbed by the cryptorchid condition...

Animals↗
PubMed1979

Management of stab wounds of the back and flank.

Abdominal stab wounds are managed on a selective basis with increasing frequency. Retroperitoneal injuries are more difficult to evaluate; hence wounds to the flank and back pose different considerations. A retrospective review of 108 patients with deep stab wounds of the flank and back was compared with a prospective study of 109 patients selectively managed with similar injuries. Physical examination was accurate in 86% of flank and 88% of back wounds. Local exploration was an effective procedure in differentiating superficial from deep wounds. Peritoneal lavage may be more accurate in flank wounds but is probably less reliable with retroperitoneal injuries. Adjunctive studies are helpful in selected patients. The incidence of negative celiotomies was reduced from 85.2% to 7.3% when the selective approach was adopted. There was no mortality or increased morbidity in the series. Although the risk of retroperitoneal injury is greater with flank and back wounds, frequent examination by the same observer combined with adjunctive studies in selected cases appears to be a safe, reliable method of managing patients with stab wounds of the back and flank.

Back↗
PubMed1979

Comparison of luteinizing hormone and prolactin levels in cycling and anestrous ewes.

Concentrations of luteinizing hormone (LH) and prolactin (Prl) in the serum of anestrous and cycling ewes were compared. The concentration of LH in serum and the frequency of episodic releases of LH were lower in anestrous than in cycling ewes. Concentrations of LH in serum rose as rapidly after ovariectomy of anestrous ewes as after ovariectomy of cycling ewes. Prl levels were higher during anestrus than at any stage of the estrous cycle; however, high Prl levels were not necessarily associated either with low LH levels or the absence of episodic release of LH. These data suggest: (1) that anestrus is not due to a reduction in the intrinsic ability of the hypothalamo-hypophyseal system to secrete LH, and (2) that high Prl levels may be a symptom rather than a cause of seasonal anestrus.

Animals↗