Estimation of serum gentamicin by quenching fluoroimmunoassay

A new type of non-isotopic immunoassay, applied to the determination of serum gentamicin, is reported. The method is based on partial quenching of fluorescence observed when fluorescein-labelled gentamicin is bound by anti-gentamicin serum. The fluorescence intensity of the labelled gentamicin in an unseparated immunoassay incubation mixture therefore serves to indicate the extent of binding, which is related to the amount of competing unlabelled gentamicin present. Precision and accuracy are shown to be similar to those of the best existing methods for gentamicin, while the new assay is more rapid and technically simpler, and avoids the use of expensive radio-chemicals with their attendant health hazard. Assays of patient samples correlate with established bioassay and polarisation fluoroimmunoassay methods.     

The surgical management of catheter injuries of the brachial artery

In 84 patients the wrist pulses were lost after diagnostic left heart catheterization via the brachial artery. Sixty-six of these patients underwent surgical exploration of the brachial artery for restoration of pulsatile arterial flow to the hand. This aim was achieved in 64 instances. In all cases, the artery was found to be occluded by fresh thrombus. In 36 patients, balloon thrombectomy and accurate arterial closure were successful. In the remainder, in addition to thrombectomy, indentification of an area of damage to the arterial wall required additional surgical measures, usually in the form of resection and anastomosis. The surgical approach to this problem and the importance of the recognition and treatment of arterial wall damage by the catheter are stressed in this paper.     

Analysis of theoretical behavior of a proposed zero-order drug delivery system

An analysis of the theoretical behavior of a proposed zero-order drug delivery system is presented. Equations describing drug release with time are developed using a physically realistic model. The theory agrees well with experimental data and indicates that drug release from the device is nearly, although not rigorously, zero order.     

Studies on the neurophysiology of the vas deferens

In order to investigate the mechanism of sperm transport along the genital ducts, intraluminal pressure of isolated segments of the vas deferens was recorded in vivo. Responses to filling and mechanical as well as pharmacologic and electric stimulation of the autonomic nervous system were monitored. Contraction waves were initated in response to the stretch of filling and from mechanical stimulation. Pharmacologic response was variable. Low doses of alpha-adrenergic stimulant produced an increase in frequency of the contraction wave. Large doses of the same drug induced stroking contraction of the entire vas. alpha-Blocking drugs did not alter the rhythmic activity of the vas. beta-Adrenergic stimulation blocked peristaltic activity while administration of parasympathomimetic drugs increased the force of contraction. Electric stimulation of the hypogastric nerve produced strong sustained contractions. These data suggest that, whenever stretched, the vas deferens responds by regular peristaltic waves of low amplitude. These peristaltic waves can be enhanced by sympathomimetics or electric stimulation of the sympathetic system. The contents of the vas are propulsed into the urethra through strong rhythmic contractions of the entire vas.     

The renal medulla and mechanisms of hypertension in the spontaneously hypertensive rat

A significant number of offspring from brother-sister matings of NIH-Okamoto-Aoki spontaneously hypertensive rats (SHRs) were found to be normotensive at 20 weeks of age. Over 20% of the animals that were hypertensive at this age had mild-to-moderate unilateral hydronephrosis at the time of sacrifice. In over 90% of the rats that did not develop hypertension spontaneously, ligation of one ureter raised blood pressure above 150 mm Hg within 2 weeks. In those rats made hypertensive by obstructing one ureter and in those that developed hypertension with accompanying naturally occurring hydronephrosis, subcutaneous implants of fragmented renal medulla from unrelated normal rats decreased blood pressure to normotensive levels. In contrast, medullary implants had no significant effect in rats developing hypertension spontaneously without hydronephrosis. Renal inner medullary plasma flow was low in the obstructed kidneys of hydronephrotic hypertensive SHRs but was elevated in the kidneys of nonhydronephrotic hypertensive SHRs. The hypertension in hydronephrotic SHRs appears to be related to an impairment of the antihypertensive function of the renal medulla. Such an impairment of medullary antihypertensive function does not appear to play a significant role in the hypertension in SHRs without hydronephrosis.     

Suxamethonium-induced porcine malignant hyperthermia

Metabolic, haemodynamic and neuroendocrine responses to suxamethonium (SCh) were measured in five normal swine and five swine susceptible to malignant hyperthermia (MH), to compare the responses with those previously reported for halothane. Following SCh, the onset of MH was sooner and more abrupt than following halothane. The maximal changes in aerobic metabolism and body temperature sere similar, while the changes in lactate, potassium, hydrogen ion and catecholamine concentrations were smaller than those observed following halothane. These results are discussed in terms of the action of chemical depolarizing drugs such as suxamethonium and acetylcholine. The propagated muscle action potentials produce an increase in the free intracellular calcium concentration which may be self-regenerative, but which may become uncontrollable because of the peculiarities of MH that effect the calcium pump or storage areas.     

Chromosome breaks and sister chromatid exchanges in albinos in Nigeria

The prevalence of squamous cell carcinoma of the skin in albinos reaches approximately 90% in patients over 20 years of age in the vicinity of Enugu, Nigeria. Chromosome breaks and sister chromatid exchanges (SCE) were evaluated in tyrosinase-positive oculocutaneous albinos and pigmented controls of Ibo extraction who were life-long residents of Nigeria. No difference in the frequency of chromosomal breaks in 14 albinos compared to 6 pigmented controls, and no differences in the frequency of SCE in 9 albinos compared to 3 controls could be detected. Increased chromosomal abnormalities in lymphocytes do not appear to be assoicated with albinism or fulminating skin cancer present in albinos in the tropics.