In this book Professor Holmes discusses some of the evidence relating to one of the most baffling problems yet recognized by biologists-the factors involved in the regulation of growth and form. A wide range of possible influences, from enzymes to cellular competition, is considered. Numerous experiments and theories are described, with or without bibliographic citation. There is a list of references for each chapter and an index. The subject from a scientific standpoint is an exceedingly difficult one, for the reason that very little indeed is understood regarding such phenomena as differentiation. It follows that the problem offers fine opportunities for intellectual jousting by mechanists and vitalists, that hypotheses and theories must often be the weapons of choice, and philosophy the armor. Professor Holmes gives us a good seat from which to watch the combats, explains clearly what is going on, and occasionally slips away to enter the lists himself. This stereoscopic atlas of anatomy was designed as an aid in teaching neuro-anatomy for beginning medical students and as a review for physicians taking Board examinations in Psychiatry and Neurology. Each plate consists of a pair of stereoscopic photographs and a labelled diagram of the important parts seen in the photograph. Perhaps in this day of scarcity of materials, particularly of human brains hardened for dissection, photographs of this kind conceivably can be used as a substitute. Successive stages of dissection are presented in such a fashion that, used in conjunction with the dissecting manual, a student should be able to identify most of the important components of the nervous system without much outside help. The area covered is limited to the gross features of the brain and brain stem and perhaps necessarily does not deal with any of the microscopic structure. So much more can be learned from the dissection of the actual brain that it is doubtful if this atlas would be useful except where brains are not available. A good deal of effort has been spent on the preparation of this atlas, with moderately successful results.

The Integrative Action of the Nervous System.

1.

The influence of mechanosensory stimulation of a second segment swimmeret upon the abdominal postural program was examined in an isolated abdominal nerve cord-swimmeret preparation. The swimmeret was stimulated in several different ways to assess the extent of influence exerted on abdominal positioning.




2.

Localized tactile stimulation of the swimmeret surface with a mechanical probe usually generated flexion inhibition where the flexor inhibitor (f5) was activated while the small and medium flexor excitors were inhibited (Figs. 4, 5). Flexion inhibition was much stronger in females than males. In 50% of the animals a weak flexion excitation was seen (Fig. 6). After 3–6 hours the response of one-third of these preparations changed to flexion inhibition.




3.

Strong manual stimulation of the swimmeret surface inhibited all of the flexor excitors (f1, f2, f3, f4, and f6) while exciting the inhibitor f5 and increasing extensor activity (Fig. 11). Similar extension responses were observed in both sexes.




4.

Repeated tactile stimulation of the swimmeret surface elicited a response similar to that evoked during manual stimulation. The strongest extension response was produced at 2 Hz which falls within the normal range of swimmeret beating in intact lobsters (Figs. 8, 9). Similar extension responses were also obtained during spontaneous swimmeret beating and rhythmic manual movement of the swimmeret (Fig. 10A, C).




5.

The interganglionic spread of postural responses and their long latencies imply the involvement of a population of interneurons that are affected by tactile stimulation of the swimmeret and which in turn form part of the integrative network that controls abdominal posture.

Tactile stimulation of the swimmeret alters motor programs for abdominal posture in the lobster Homarus americanus.

Exposure of the body to microgravity during space flight causes a series of well-documented changes in Ca2+ metabolism, yet the cellular and molecular mechanisms leading to these changes are poorly understood. Calbindins, vitamin D-dependent Ca2+ binding proteins, are believed to have a significant role in maintaining cellular Ca2+ homeostasis. In this study, we used biochemical and immunocytochemical approaches to analyze the expression of calbindin-D28k and calbindin-D9k in kidneys, small intestine, and pancreas of rats flown for 9 d aboard the space shuttle. The effects of microgravity on calbindins in rats from space were compared with synchronous Animal Enclosure Module controls, modeled weightlessness animals (tail suspension), and their controls. Exposure to microgravity resulted in a significant and sustained decrease in calbindin-D28k content in the kidney and calbindin-D9k in the small intestine of flight animals, as measured by enzyme-linked immunosorbent assay (ELISA). Modeled weightlessness animals exhibited a similar decrease in calbindins by ELISA. Immunocytochemistry (ICC) in combination with quantitative computer image analysis was used to measure in situ the expression of calbindins in the kidney and the small intestine, and the expression of insulin in pancreas. There was a large decrease of immunoreactivity in renal distal tubular cell-associated calbindin-D28k and in intestinal absorptive cell-associated calbindin-D9k of space flight and modeled weightlessness animals compared with matched controls. No consistent difference in pancreatic insulin immunoreactivity between space flight, modeled weightlessness, and controls was observed. Regression analysis of results obtained by quantitative ICC and ELISA for space flight, modeled weightlessness animals, and their controls demonstrated a significant correlation. These findings after a short-term exposure to microgravity or modeled weightlessness suggest that a decreased expression of calbindins may contribute to the disorders of Ca2+ metabolism induced by space flight.

Calbindins decreased after space flight

A platform was lowered from beneath suspended crayfish, Cherax destructor, to evoke slow abdominal extension. The movements were filmed and the length between segments plotted as a function of time. Unlike abdominal flexion, which starts posteriorly and progresses anteriorly, extension occurs at all joints simultaneously. Although the duration of extension varied from trial to trial for an individual, the movement was organised in a stereotyped manner: the abdomen achieved a consistent position for any given proportion of the time for complete extension. We examined the role of the abdominal muscle receptor organs (MROs) in extension by cutting the nerves of selected MROs to abolish their input. The extension movement was measured before and after nerve section for animals with either unloaded or loaded abdomens. Removal of MRO input had no significant effect on extension of the unloaded abdomen. In animals with a loaded abdomen, the extension at joints spanned by sectioned MROs was slowed, whereas that at joints with intact MROs was not. The findings are consistent with the hypothesis that the MRO is an error detector in a servo-loop controlling abdominal position. The results provide the first demonstration that this load-compensating reflex loop operates during naturally evoked extension of the abdomen under constant load.

https://courses.cit.cornell.edu/bionb491/labresources/week3,%20Feb%202-4/McCarthy&Macmillian'95.pdf

The role of the muscle receptor organ in the control of abdominal extension in the crayfish cherax destructor

In a multiganglionic preparation of the lobster abdominal nerve cord, composed of the first through fifth ganglia (A1-A5) and attached second swimmeret, tactile stimulation of the cuticular surface of the swimmeret initiates a postural motor program in A2 for abdominal extension, whereas deflection of feathered hair sensilla that fringe the swimmeret rami does not affect postural motor activity recorded from A2 (Kotak and Page, 1986a). This report demonstrates that partial isolation of A2 from adjacent abdominal ganglia by sectioning the A1-A2 or the A2-A3 connectives both increases the strength of the extension response evoked by cuticular stimulation and disinhibits a postural flexion inhibition response initiated by feathered hair stimulation. Complete isolation of A2, by cutting the A1-A2 and the A2-A3 connectives, further increases the strength of these postural responses. Intersegmental inhibition of these responses originates in the ganglia adjacent to A2, since mechanoresponsiveness of A2 is not affected by resection of a more distant connective (A3-A4). These results provide evidence for the presence in adjacent abdominal ganglia of intersegmental interneurons that regulate the access of swimmeret sensory activity to the postural motor neurons in A2.

Intersegmental modulation of abdominal postural responses initiated by mechanostimulation of the swimmeret in lobster.

Publisher Summary This chapter focuses on calbindin D 28K gene expression in aging and neurodegenerative diseases. The study described in the chapter has permitted an analysis of the role that changes in calbindin D 28K gene expression may play in the etiology and pathogenesis of neurodegeneration in the brain, such as Huntington's, Parkinson's, and Alzheimer's diseases. A method of molecular cloning of calbindin D 28K described in the chapter resulted in the isolation of a cloned calbindin D 28K cDNA via direct immunological screening of a mouse cerebellar λgt11 bacterial expression library. The calbindin D 28K cDNA could then be radiolabeled directly and utilized as a probe for detection of calbindin D 28K mRNA (slot-blot and Northern blot analyses) or converted to radiolabeled cRNA transcripts to detect calbindin D 28K mRNA at the cellular level by in situ hybridization. Slot-blot and Northern blot hybridization analyses revealed that in each disease entity, the brain area that is particularly affected and used as a hallmark for the neuropathological changes exhibits a significant reduction in calbindin D 28K gene expression.

Calbindin D28K Gene Expression in Neurodegenerative Diseases

SUMMARY An intersegmental reflex initiated by flexing a crayfish leg at the merocarpal joint was examined by recording reflex response latencies of cephalic, thoracic and abdominal muscles. The first response was an intrasegmental resistance reflex in the extensor muscle of the stimulated leg. Spread of the intersegmental reflex occurred in both cephalic and caudal directions. Activation of the cephalic appendages occurred first (antennal levators, with latencies of 14-18 ms) while the abdominal musculature was activated last (superficial extensors, with latencies of 51-62ms). Shift of the stimulus site from the second to the fifth leg resulted in shorter latencies of the fifth leg and abdominal muscle responses while the latency for second leg extensor muscle discharge increased. Low correlation coefficients between the response latencies of pairs of cephalic and abdominal muscles, and thoracic and abdominal muscles, indicate that reflex pathways which initiate the abdominal responses are different from those that evoke the cephalic and thoracic responses. High correlation coefficients indicate common reflex pathways for activating either ipsilateral or contralateral pairs of extensors or flexors in the second and fifth legs. High correlations suggesting common reflex pathways or cross-coupling were also obtained for bilateral pairs of abdominal extensors. Low correlation coefficients for the response latencies of paired muscles indicate separate reflex pathways for (1) bilaterally homologous leg muscles and (2) first-fifth segment abdominal extensors. Surgical isolation of the supraoesophageal ganglion from the ventral nerve cord eliminated the responses of the antennal levators while producing a substantial increase in the response latencies of both maxilliped extensors and the contralateral second leg extensor and flexor, as well as a small but significant decrease in the contralateral first abdominal extensor. The synaptic input zones of the interneurones that mediate the thoracic and abdominal responses are located in the ventral nerve cord and not in the supraoesophageal ganglion.

Anthony M. Iacopino

Papers

Calbindin D28K Gene Expression in Neurodegenerative Diseases

Temporal and spatial spread of an intersegmental reflex in crayfish