Justus Liebig and animal chemistry.

Justus Liebig was one of the individuals making chemistry almost a German monopoly in the 19th century. At Giessen he established the first organic chemistry laboratory and offered a systematic course for training new chemists. His comprehensive survey of plant nutrition changed the nature of scientific agriculture. In a study of animal chemistry, Liebig treated physiologic processes as chemical reactions and inferred the transformations from the chemical properties of the elements and compounds in laboratory reactions. He constructed hypothetical chemical equations derived from the formulae of the participating compounds. Liebig generalized that all organic nitrogenous constituents of the body are derived from plant protein and demonstrated how the application of quantitative methods of organic chemistry can be applied to the investigation of the animal organism. Liebig's theories were attractive, but his method of converting one substance to another by moving atoms around on paper was speculative because of the lack of knowledge as to how the elements were arranged. His dynamic personality helped win widespread acceptance by many, but others were antagonized by his wishful thinking and speculative excesses. Liebig's views on catalysis and fermentation brought him into a controversy with Louis Pasteur. Liebig's Animal Chemistry stimulated an interest in clinical chemistry because it introduced a quantitative method into physiological chemistry. However, the isolated pieces of test results on blood and urine were unconnected and did not fit anywhere. Physicians found that chemistry was not helpful at the bedside and they lost interest in its application.

Amiloride reduces stroke and renalinjury in stroke-prone hypertensive rats.

BACKGROUND: We previously reported that the mineralocorticoid receptor antagonists spironolactone and eplerenone markedly reduce proteinuria and vascular injury in saline-drinking stroke-prone spontaneously hypertensive rats (SHRSP). Presently, we examined whether amiloride, an epithelial sodium channel blocker, would also protect against pathology in these rats. METHODS: In acute studies, saline-drinking SHRSP (n = 5) were instrumented with radiotelemetry blood pressure (BP) probes and housed in metabolic cages. Mean arterial pressure and electrolyte excretion were quantified over the 24-h period after oral administration of vehicle or amiloride at 1, 3, 10, and 30 mg/kg. In a survival study, 8.5-week-old SHRSP were either untreated (control, n = 7) or given amiloride (1 mg/kg/day, n = 8) in their 1% NaCl drinking solution. Systolic BP, proteinuria, body weight, and renal and brain histopathology were assessed. RESULTS: Acute amiloride treatment did not alter urine output, urinary electrolyte excretion, and sodium-to-potassium ratio or body weight. The mean arterial pressure was unaffected except for a 16-mm Hg reduction at 30 mg/kg (P <.01). Six of eight SHRSP chronically treated with amiloride survived through 20 weeks of age, whereas all control SHRSP died by 16.4 weeks (P <.0001). Amiloride delayed proteinuria (119 +/- 24 v 15 +/- 2 mg/day, P <.002) with no significant effect on systolic BP (228 +/- 6 v 217 +/- 4 mm Hg) at 12 weeks of age. CONCLUSIONS: These findings suggest that interference with sodium channel function, perhaps at sites other than the kidney epithelium, may play a role in protecting against the evolution of cerebral and renal vascular injury in saline-drinking SHRSP.

Estrogen promotes microvascular pathology in female stroke-prone spontaneously hypertensive rats.

Estrogen produces both beneficial and adverse effects on cardiovascular health via mechanisms that remain unclear. Stroke-prone spontaneously hypertensive rats (SHRSP) maintained on Stroke-Prone Rodent Diet and 1% NaCl drinking water (starting at 8 wk of age) rapidly develop stroke and malignant nephrosclerosis that can be prevented, despite continued hypertension, by drugs targeting angiotensin II and aldosterone actions. This study evaluated estrogen's effects in the SHRSP model. Female SHRSP that were sham operated (SHAM), ovariectomized (OVX) at 4 wk of age, or OVX and treated with estradiol benzoate (E2,30 microg x kg-1 x wk-1) were studied. In a survival protocol, OVX rats lived significantly longer (15.1 +/- 0.3 wk) compared with SHAM (13.6 +/- 0.2 wk) or OVX+E2 rats (12.4 +/- 0.2 wk). In a protocol in which animals were matched for age, at 11.5 wk, terminal systolic blood pressure and urine protein excretion were elevated in SHAM and OVX+E2 rats compared with OVX rats; blood urea nitrogen, renal microvascular and glomerular lesions, and plasma renin concentration were elevated in OVX+E2 relative to SHAM or OVX rats. In a survival protocol using intact female SHRSP, treatment with an antiestrogen (tamoxifen, 7 mg.kg-1.wk-1) prolonged survival by >2 wk compared with controls (P < 0.01). The data indicate that estrogen promotes microangiopathy in the kidney and stroke in saline-drinking SHRSP.

William Prout: early 19th century physician-chemist.

In the early 19th century, the discoveries of new substances in the healthy and diseased body spawned a search for chemical explanations for physiologic phenomena to guide medical diagnosis and control therapy. William Prout's work on the nature and treatment of diseases of the urinary organs established his reputation as one of Britain's most distinguished physiological chemists. Prout was very skeptical of chemical remedies because of possible side effects, but he suggested iodine treatment for goiter. He emphasized that a satisfactory diet should include carbohydrates, fats, protein, and water. In 1824, he showed that the acid of the gastric juice was hydrochloric acid. Prout applied chemical methods and reasoning to physiology and was criticized for his view that the body's vital functions could be explained by chemistry. His remedy for lack of progress in animal chemistry was for physiologists to become chemists. Prout stimulated much discussion on atomic theory by his hypothesis that the atomic weights of all chemical elements are whole-number multiples of the atomic weight of hydrogen and that the chemical elements were condensed from hydrogen atoms.

Insulin: discovery and controversy.

During the first two decades of the 20th century, several investigators prepared extracts of pancreas that were often successful in lowering blood sugar and reducing glycosuria in test animals. However, they were unable to remove impurities, and toxic reactions prevented its use in humans with diabetes. In the spring of 1921, Frederick G. Banting, a young Ontario orthopedic surgeon, was given laboratory space by J.J.R. Macleod, the head of physiology at the University of Toronto, to investigate the function of the pancreatic islets. A student assistant, Charles Best, and an allotment of dogs were provided to test Banting's hypothesis that ligation of the pancreatic ducts before extraction of the pancreas, destroys the enzyme-secreting parts, whereas the islets of Langerhans, which were believed to produce an internal secretion regulating sugar metabolism, remained intact. He believed that earlier failures were attributable to the destructive action of trypsin. The name "insuline" had been introduced in 1909 for this hypothetic substance. Their experiments produced an extract of pancreas that reduced the hyperglycemia and glycosuria in dogs made diabetic by the removal of their pancreases. They next developed a procedure for extraction from the entire pancreas without the need for duct ligation. This extract, now made from whole beef pancreas, was successful for treating humans with diabetes. Facilitating their success was a development in clinical chemistry that allowed blood sugar to be frequently and accurately determined in small volumes of blood. Success with purification was largely the work of J.B. Collip. Yield and standardization were improved by cooperation with Eli Lilly and Company. When the Nobel Prize was awarded to Banting and Macleod for the discovery of insulin, it aggravated the contentious relationship that had developed between them during the course of the investigation. Banting was outraged that Macleod and not Best had been selected, and he briefly threatened to refuse the award. He immediately announced that he was giving one-half of his share of the prize money to Best and publicly acknowledged Best's contribution to the discovery of insulin. Macleod followed suit and gave one-half of his money award to Collip. Years later, the official history of the Nobel Committee admitted that Best should have been awarded a share of the prize.

Effects of monocrotaline on endothelial nitric oxide synthase expression and sulfhydryl levels in rat lungs.

The nitric oxide-cyclic guanosine monophosphate signal-transduction mechanism plays a key role in the regulation of vascular tone and structure. Monocrotaline-induced pulmonary hypertension is associated with low bioavailability of nitric oxide. To characterize the mechanism(s) involved in this dysfunction, rats received a single subcutaneous injection of monocrotaline, normal saline (control), or monocrotaline plus daily L-arginine, a precursor of nitric oxide, in drinking water. Pulmonary artery pressure and right ventricular hypertrophy were assessed 2 weeks later. In addition, the authors evaluated the expression of endothelial nitric oxide synthase messenger RNA, endothelial nitric oxide synthase protein, cyclic guanosine monophosphate, and sulfhydryl levels in the lungs. Sulfhydryls are needed for the dynamic modulation of soluble guanylate cyclase by nitric oxide, which results in cyclic guanosine monophosphate formation. L-arginine treatment did not attenuate monocrotaline-induced pulmonary hypertension or right ventricular hypertrophy. Monocrotaline did not alter the expression of endothelial nitric oxide synthase messenger RNA or endothelial nitric oxide synthase protein in the lungs. Protein-bound sulfhydryls (28 +/- 5 vs. 75 +/- 16 pmol/microg protein) and cyclic guanosine monophosphate (0.63 +/- 0.05 vs. 1.06 +/- 0.017 pmol/microg protein) levels in the monocrotaline group were significantly low compared with controls. The low sulfhydryl levels, an indicator of oxidant stress, may account for the impaired availability of bioactive nitric oxide and low cyclic guanosine monophosphate levels. These results suggest that oxidative stress may, in part, contribute to the pathogenesis of pulmonary hypertension in the monocrotaline model.

Clinical chemistry since 1800: growth and development.

The 19th and 20th centuries witnessed the growth and development of clinical chemistry. Many of the individuals and the significance of their contributions are not very well known, especially to new members of the profession. This survey should help familiarize them with the names and significance of the contributions of physicians and chemists such as Fourcroy, Berzelius, Liebig, Prout, Bright, and Rees. Folin and Van Slyke are better known, and it was their work near the end of the second decade of the 20th century that brought the clinical chemist out of the annex of the mortuary and into close relationship with the patient at the bedside. However, the impact on clinical chemistry and the practice of medicine by the 1910 exposé written by Abraham Flexner is not as well known as it deserves to be, nor is the impetus that World War I gave to the spread of laboratory medicine generally known. In the closing decades of the 20th century, automated devices produced an overabundance, and an overuse and misuse, of testing to the detriment of careful history taking and bedside examination of the patient. This is attributable in part to a fascination with machine-produced data. There was also an increased awareness of the value of chemical methods of diagnosis and the need to bring clinician and clinical chemist into a closer partnership. Clinical chemists were urged to develop services into dynamic descriptions of the diagnostic values of laboratory results and to identify medical relevance in interpreting significance for the clinician.